The wire size for 100 ft run varies based on the load current, voltage, and conductor material. At 240V single-phase with copper conductors, common wire sizes at 100 ft are 12 AWG for 15A, 10 AWG for 20A, 8 AWG for 30-40A, 6 AWG for 50-60A, and progressively larger sizes for higher currents. This article provides complete reference tables for wire size at 100 ft across all common loads, voltages, and conductor materials, plus quick-lookup widget, application examples for common 100 ft residential installations, wire type selection guidance, and analysis of why 100 ft is the critical distance where voltage drop becomes a significant sizing consideration.

Across thousands of Southwire and Cerrowire orders shipped from IB Lighting nationwide, our electrician-led team advises DIY installers and licensed electricians on wire sizing decisions including the distance-driven analysis that determines whether a code-minimum wire size is adequate for longer residential runs. Founded in 2013 by a licensed Master Electrician with field experience across DTE Energy and Consumers Energy projects in Michigan, IB Lighting resells the full Southwire and Cerrowire electrical wire and cable lineup.

This article provides the wire size for 100 ft run reference tables that we use to help buyers verify wire size decisions before purchasing, using calculations aligned with the current National Electrical Code (NFPA 70) and industry practice from the International Association of Electrical Inspectors.

The Fast Answer: Wire Size for 100 ft Run

For a 100 ft run at 240V single-phase with copper conductors and 3 percent maximum voltage drop, the required wire sizes are: 14 AWG for loads under 10 amps, 12 AWG for 15 amp loads, 10 AWG for 20 amp loads, 8 AWG for 30-40 amp loads, 6 AWG for 50-60 amp loads, 4 AWG for 80 amp loads, 3 AWG for 100-125 amp loads, 2 AWG for 150 amp loads, and 1 AWG for 200 amp loads. For 120V circuits, wire sizes are approximately one to two sizes larger due to worse voltage drop percentage at lower voltage.

The complete wire size specification for 100 ft runs

The complete specification for a wire size for 100 ft run installation includes: wire gauge sized for the specific load current at 3 percent maximum voltage drop, wire type appropriate for installation environment (NM-B indoor, THWN-2 in conduit outdoor, UF-B direct burial), conductor material (copper or aluminum with material-specific size adjustments), and appropriate breaker size matching both wire ampacity and load requirements.

Voltage matters significantly at 100 ft

The wire size for 100 ft run at 120V is significantly larger than at 240V for the same amperage load because voltage drop as a percentage of source voltage is twice as bad at 120V compared to 240V for the same absolute voltage drop. This is why running 240V circuits over long distances is preferred when possible, and why most long-distance residential circuits (subpanel feeders, well pumps, EV chargers) operate at 240V.

Material matters less but still meaningful

The wire size for 100 ft run with aluminum conductors is typically one size larger than copper for the same load and voltage. Aluminum resistance is approximately 60 percent higher than copper, requiring the size upgrade to maintain equivalent voltage drop performance. On long runs, the cost savings of aluminum wire can partially offset the required size upgrade.

Why 100 ft Is the Critical Distance Threshold

100 ft has become the recognized threshold for “long-distance” residential wiring for several practical reasons that make it an important benchmark for wire sizing decisions.

Common installation distance

100 ft matches the typical distance for many common residential installations: detached garage subpanel feeders, well pumps at typical yard well locations, outdoor equipment like hot tubs and pool pumps, EV charger installations at distant garage locations, HVAC condenser circuits for houses with the electrical panel on the opposite side, and workshop or shed circuits in rural properties.

Voltage drop becomes noticeable

At distances under 50 feet, voltage drop is typically negligible for most residential circuits at their designed load current. At 100 feet, voltage drop becomes noticeable for many common loads. This is the distance where wire size upgrades based on voltage drop start becoming necessary rather than optional, and where the NEC 3 percent recommendation begins driving wire size larger than ampacity requirements alone would specify.

Psychological benchmark for DIY installers

100 ft is the mental benchmark most DIY installers use to think about “long distance” wiring. Shorter runs (under 50 ft) feel routine and standard wire sizes work well. Longer runs (over 150 ft) clearly need special attention. The 100 ft threshold sits at the boundary where installers begin asking whether standard wire sizes are adequate.

Practical planning distance

Many wire products are sold in reels of 50, 100, and 250 ft lengths. A single 100 ft reel of the appropriate wire size handles a complete 100 ft installation with minimal waste and no splices in the run. This makes 100 ft a natural planning distance for wire purchases, reinforcing its role as a standard reference length.

The NEC Math Behind Wire Sizing at 100 ft

Understanding the calculation that determines wire size for 100 ft run helps clarify the specific values in the reference tables and enables verification of unusual load or voltage combinations.

The voltage drop formula applied to 100 ft

The single-phase voltage drop formula VD = (2 × K × I × L) / CM applied to 100 ft with copper conductors becomes VD = (2 × 12.9 × I × 100) / CM = (2,580 × I) / CM. This simplified formula produces voltage drop in volts for any current and conductor cross-section. For aluminum conductors, K is 21.2 instead of 12.9, producing VD = (4,240 × I) / CM.

Solving for required circular mils at 3 percent drop

Setting VD = 3 percent of source voltage and solving for required conductor circular mils: For 240V, VD max = 7.2V, so CM required = (2,580 × I) / 7.2 = 358.3 × I. For 120V, VD max = 3.6V, so CM required = (2,580 × I) / 3.6 = 716.7 × I. These formulas give the minimum circular mils needed for 3 percent voltage drop at 100 ft for any current in amps.

Matching required CM to wire gauge

Once required circular mils are calculated, match to the smallest standard wire size that meets or exceeds the requirement. Standard wire size circular mils: 14 AWG has 4,110 CM, 12 AWG has 6,530 CM, 10 AWG has 10,380 CM, 8 AWG has 16,510 CM, 6 AWG has 26,240 CM, 4 AWG has 41,740 CM, 3 AWG has 52,620 CM, 2 AWG has 66,360 CM, 1 AWG has 83,690 CM, 1/0 AWG has 105,600 CM, 2/0 AWG has 133,100 CM, 3/0 AWG has 167,800 CM, and 4/0 AWG has 211,600 CM.

Verifying ampacity requirements are also met

After determining wire size from voltage drop calculation, verify the wire size also meets ampacity requirements per NEC Table 310.16 and the small conductor rule per NEC 240.4(D). For most 100 ft runs with typical loads, voltage drop is the limiting factor and produces adequate ampacity. For short circuits with high current loads, ampacity may drive wire size selection above voltage drop requirements.

Wire Size for 100 ft Run at 240V (Copper) Reference Table

The following table shows recommended copper wire sizes for 100 ft runs at 240V single-phase with 3 percent maximum voltage drop. Match your load current to find the required wire size and typical breaker size.

240V single-phase copper wire sizes at 100 ft

For 10 amp load, 14 AWG copper with 15 amp breaker is adequate. For 15 amp load, 12 AWG copper with 20 amp breaker. For 20 amp load, 10 AWG copper with 25 amp breaker. For 30 amp load, 8 AWG copper with 40 amp breaker (10 AWG would be marginal at exactly 30 amps). For 40 amp load, 8 AWG copper with 40 amp breaker. For 50 amp load, 6 AWG copper with 50 amp breaker.

240V copper for higher amperage loads at 100 ft

For 60 amp load, 6 AWG copper with 60 amp breaker. For 80 amp load, 4 AWG copper with 80 amp breaker. For 100 amp load, 3 AWG copper with 100 amp breaker. For 125 amp load, 3 AWG copper with 125 amp breaker (marginal, better with 2 AWG). For 150 amp load, 2 AWG copper with 150 amp breaker. For 200 amp load, 1 AWG copper with 200 amp breaker.

Common load examples at 240V at 100 ft

Common loads for 240V circuits at 100 ft include: water heater (30A) requiring 8 AWG copper, electric dryer (30A) requiring 8 AWG copper for the longer voltage-drop-driven size, hot tub (50A) requiring 6 AWG copper, EV charger (48A continuous) requiring 6 AWG copper 90 degree rated, central AC 3 ton (25-30A) requiring 8 AWG copper, garage subpanel 60A requiring 6 AWG copper, and garage subpanel 100A requiring 2 or 3 AWG copper.

Consideration for continuous loads

For continuous loads including EV chargers, water heaters running continuous, and electric HVAC equipment, the load current in the voltage drop calculation should be the maximum continuous current, not the intermittent peak. This ensures the wire size accounts for the extended-duration current flow that causes cumulative voltage drop effects during long charging or heating cycles.

Wire Size for 100 ft Run at 120V (Copper) Reference Table

The following table shows recommended copper wire sizes for 100 ft runs at 120V single-phase with 3 percent maximum voltage drop. Wire sizes are notably larger than 240V equivalents due to worse voltage drop percentage at lower voltage.

120V single-phase copper wire sizes at 100 ft

For 10 amp load at 120V, 10 AWG copper with 15 amp breaker is required (14 AWG would exceed 3 percent voltage drop). For 15 amp load, 8 AWG copper with 15 amp breaker (or accept slightly higher voltage drop with 10 AWG on 20 amp breaker). For 20 amp load, 8 AWG copper with 20 amp breaker. For 30 amp load, 6 AWG copper with 30 amp breaker.

Why 120V circuits at 100 ft need larger wire

The 3 percent voltage drop recommendation is a percentage of source voltage. At 240V, 3 percent = 7.2V. At 120V, 3 percent = 3.6V. Since the voltage drop in the wire depends only on the current and wire resistance (not source voltage), the same wire produces the same absolute voltage drop regardless of source voltage. This means the drop becomes twice as bad as a percentage at 120V compared to 240V.

Common 120V load examples at 100 ft

Common 120V loads that might run 100 ft include: outdoor lighting circuits (15A) which typically require upgrade to 8 AWG copper rather than standard 14 AWG for indoor use, garage outlet circuits (20A) requiring 8 AWG copper rather than standard 12 AWG, well pump control circuits (often 120V pump control power), and remote outbuilding lighting circuits.

When to convert 120V to 240V for long runs

For long 120V runs approaching or exceeding 100 ft, consider whether the load can be served by a 240V circuit instead. Many appliances that operate on 120V could operate on 240V with equipment change, and the smaller wire required for 240V often reduces total installation cost. This is common for well pumps where 120V and 240V versions of the same pump are typically available at similar prices.

Wire Size for 100 ft Run with Aluminum Conductors

Aluminum conductors require different wire size selections than copper for the same 100 ft installation due to aluminum’s higher electrical resistance.

Aluminum size adjustment from copper

Aluminum wire size for the same voltage drop performance is typically one AWG size larger than copper. For 60A copper (6 AWG) equivalent, use 4 AWG aluminum. For 100A copper (3 AWG) equivalent, use 1 AWG aluminum. For 200A copper (1 AWG) equivalent, use 3/0 aluminum. This size upgrade compensates for aluminum’s 60 percent higher electrical resistance.

240V aluminum wire sizes at 100 ft

For 240V single-phase circuits at 100 ft with aluminum: 30A load requires 6 AWG aluminum, 50A load requires 4 AWG aluminum, 60A load requires 4 AWG aluminum, 100A load requires 1 AWG aluminum, 125A load requires 1/0 aluminum, 150A load requires 2/0 aluminum, and 200A load requires 3/0 aluminum. These sizes account for both ampacity and voltage drop at 3 percent maximum.

When aluminum makes sense at 100 ft

Aluminum wire makes economic sense at 100 ft when the load is high enough (typically 60A and above) that copper wire cost becomes significant. For a 100A subpanel feeder at 100 ft, copper 3 AWG might cost 4-6 dollars per foot while aluminum 1 AWG costs 2-3 dollars per foot. Total wire cost savings of 100-300 dollars for the 100 ft run can offset the slightly higher installation complexity of aluminum.

Aluminum installation considerations

Aluminum installations require antioxidant compound at all termination points to prevent oxidation-related connection failures. Torque specifications for aluminum terminations must be followed carefully. All-copper terminations are not permitted with aluminum feeder conductors, so equipment must be rated for aluminum or a copper pigtail transition is required. These considerations add some installation complexity but do not affect the wire sizing itself.

Pro tip: When planning a 100 ft installation, always verify voltage drop calculation with your specific installation values rather than relying only on general tables. Ambient temperature, wire routing through insulated spaces, and specific load characteristics can affect actual voltage drop performance. Use our interactive voltage drop calculator for wire to verify wire size for your specific 100 ft installation before purchasing wire.

Ampacity vs Voltage Drop for 100 ft Runs

At 100 ft installations, both ampacity and voltage drop must be evaluated, but voltage drop typically becomes the limiting factor for most residential loads at this distance.

When voltage drop drives wire size

For most residential loads at 100 ft, voltage drop drives wire size above the ampacity minimum. Examples: A 30A circuit that would use 10 AWG for short runs (ampacity minimum) requires 8 AWG at 100 ft due to voltage drop. A 40A EV charger circuit that would use 8 AWG for short runs still requires 8 AWG at 100 ft but with less margin. A 60A subpanel feeder that would use 6 AWG for short runs still uses 6 AWG at 100 ft but approaching the voltage drop limit.

When ampacity drives wire size

For very high current loads at 100 ft where 3 percent voltage drop is not achievable with standard wire sizes, ampacity may drive selection while accepting some voltage drop violation of the NEC 3 percent recommendation. Very high current loads (150A+) may require adjustment approach where the total circuit design accepts higher voltage drop with equipment specified for lower operating voltage.

The combined 5 percent limit

NEC informational notes recommend combined feeder plus branch circuit voltage drop under 5 percent. For a 100 ft feeder with 3 percent voltage drop plus a 50 ft branch circuit with 2 percent voltage drop, total is 5 percent, which meets the combined limit. Understanding this combined limit helps make informed decisions when the 3 percent individual segment limit is challenging to meet.

Verifying both requirements

Always verify both ampacity and voltage drop requirements for 100 ft installations. Start with the ampacity-minimum wire size, then calculate voltage drop for that size. If voltage drop exceeds 3 percent, upgrade wire size until voltage drop is acceptable. Confirm the upgraded size still meets ampacity requirements (larger wire always meets smaller ampacity, so this is typically automatic).

Common Residential Applications at 100 ft Distance

The wire size for 100 ft run varies significantly by application because different applications have different current requirements, voltage requirements, and installation environments.

Detached garage subpanel feeder at 100 ft

A common 100 ft installation is a subpanel feeder to a detached garage. For a 60A garage subpanel at 100 ft, use 6 AWG copper (approaching but within voltage drop limit) or 4 AWG copper for better margin. For a 100A garage subpanel at 100 ft, use 3 AWG copper or 1 AWG aluminum. See our 100 amp garage subpanel wire sizing article for complete installation guidance.

Well pump circuit at 100 ft

Well pump circuits at 100 ft are typically limited by voltage drop rather than ampacity due to the motor starting inrush current. For a 1 HP well pump at 240V, standard 10 AWG copper handles the run current but voltage drop during motor starting may require 8 AWG copper for reliable starting. See our well pump wire sizing article for distance-driven sizing tables.

EV charger installation at 100 ft

A 48 amp Level 2 EV charger at 100 ft requires 6 AWG copper 90 degree Celsius rated for both the NEC 625.42 continuous load 125 percent factor and voltage drop performance. This is at the upper limit of 6 AWG copper for 100 ft at 48 amps continuous, so verify voltage drop specifically. See our Level 2 EV charger 48 amp wire sizing article.

Central AC condenser at 100 ft

Central AC condenser circuits at 100 ft typically use the nameplate-recommended wire size for shorter runs since the ampacity requirement is generally sufficient. For a 4 ton central AC at 100 ft, 8 AWG copper on 40 amp breaker satisfies both ampacity and voltage drop. See our 4 ton central AC wire sizing article.

Hot tub installation at 100 ft

Hot tub circuits at 100 ft use 6 AWG copper on 50 amp GFCI breaker per typical hot tub specifications. The 6 AWG wire has adequate voltage drop margin at 100 ft for the 40 amp continuous heater load. Additional bonding and disconnect requirements apply per NEC 680 regardless of wire distance.

Wire Type Selection for 100 ft Installations

Wire type selection for 100 ft installations depends on the routing environment and physical protection requirements.

NM-B (Romex) for indoor 100 ft runs

NM-B (Romex) can be used for the indoor portion of 100 ft runs when the wire routes entirely through indoor conditioned or unconditioned spaces. NM-B is not rated for outdoor, wet, or damp locations. For runs to detached structures, NM-B can only be used inside the source structure, transitioning to weather-rated wire for the outdoor portion.

THWN-2 in PVC conduit for outdoor 100 ft runs

THWN-2 individual conductors in PVC conduit provide the standard approach for outdoor 100 ft runs including runs to detached garages, sheds, and outdoor equipment. THWN-2 is rated for wet locations, and PVC conduit provides UV protection and physical protection. Larger wire sizes at 100 ft require larger conduit for adequate conduit fill per NEC 314.16.

UF-B direct burial for underground 100 ft runs

UF-B cable can be direct-buried for 100 ft runs from the source structure to detached structures. Minimum burial depth is 24 inches per NEC 300.5. UF-B is limited to 60 degree Celsius ampacity rating, which affects wire sizing for larger loads. For loads where 60 degree ampacity is limiting, use THWN-2 in PVC conduit instead.

SER cable for exposed 100 ft runs

SER (Service Entrance Cable, Round) can be used for 100 ft feeder circuits in exposed applications where the more robust jacket provides better physical protection than NM-B. SER is common for subpanel feeders and available in the larger sizes needed for 100 ft high-amperage runs. Both copper and aluminum SER are commonly available.

Choosing the Right Wire Product for Your 100 ft Run

Understanding which specific wire products fit the wire size for 100 ft run specification helps buyers select the correct product for their installation.

Southwire 100 ft reel selection

Southwire manufactures wire in standard reel lengths including 50, 100, 250, and 500 ft. For a single 100 ft installation, a 100 ft reel provides the exact length needed with minimal waste. For installations approaching 100 ft, consider a 250 ft reel for adequate excess and future use. Common Southwire 100 ft configurations include NM-B, THWN-2, UF-B, and SER cable.

Cerrowire alternatives

Cerrowire manufactures comparable wire and cable products in 100 ft reels for the same applications. Cerrowire and Southwire products are electrically equivalent and meet the same UL standards. Selection typically depends on regional availability, pricing, and personal preference. Both brands are widely accepted by electrical inspectors.

PVC conduit for outdoor 100 ft runs

1/2 inch to 2 inch PVC conduit accommodates various wire sizes per NEC 314.16 conduit fill calculations. For 100 ft outdoor runs, plan approximately 10 lengths of 10 ft conduit plus fittings. Standard PVC fittings including couplings, elbows, and adapters complete the installation. PVC conduit is UV resistant and provides physical protection.

Cost considerations at 100 ft

Wire cost at 100 ft varies significantly by wire size. Copper 10 AWG THWN-2 (typical 20-30 amp circuit): 50-80 dollars for 100 ft. Copper 6 AWG THWN-2 (typical 40-60 amp circuit): 150-250 dollars for 100 ft. Copper 2 AWG THWN-2 (typical 100-150 amp circuit): 400-600 dollars for 100 ft. Total installation cost including conduit, breakers, and disconnects adds 100-300 dollars.

Feeder Circuits vs Branch Circuits at 100 ft

The distinction between feeder circuits and branch circuits affects wire size decisions at 100 ft distances.

Feeder circuits at 100 ft

Feeder circuits (from main panel to subpanels) at 100 ft are common for detached garage subpanel installations, shed subpanels, and workshop subpanels. Feeder circuits are governed by NEC Article 215 and require 4-wire configuration (2 hots, neutral, ground) since the 2008 NEC. Feeder voltage drop should be under 3 percent per NEC 215.2(A)(1)(b) informational note.

Branch circuits at 100 ft

Branch circuits (from main panel or subpanel to individual loads) at 100 ft are common for well pumps, remote outdoor lighting, EV chargers at distant garage locations, and outbuilding circuits. Branch circuits are governed by NEC Article 210 and require 2-wire or 3-wire configuration depending on voltage and load. Branch voltage drop should be under 3 percent per NEC 210.19(A)(1) informational note.

Combined feeder plus branch at 100 ft

Some installations combine a 100 ft feeder to a detached structure subpanel plus branch circuits within the detached structure. The combined feeder plus branch voltage drop should be under 5 percent per NEC informational notes. This allows some flexibility when individual segments approach the 3 percent limit but combined drop remains acceptable.

Deciding between feeder and multiple branches

For installations serving multiple loads at a detached structure, a single feeder to a subpanel with local branch circuits is typically more efficient than multiple long branch circuits directly from the main panel. The subpanel approach allows shorter branch circuit runs with better voltage drop performance for each individual circuit, plus the flexibility of adding future circuits without pulling new wire back to the main panel.

Panel and Disconnect Considerations for 100 ft Runs

100 ft installations often involve additional panel and disconnect considerations beyond just the wire size.

Local disconnect requirements

Circuits serving specific equipment types require local disconnects per various NEC articles. Central AC per NEC 440.14 requires disconnect within sight. Well pumps often require disconnect within sight per NEC 430.109. Hot tubs require disconnect at least 5 feet from tub per NEC 680.42. These disconnect requirements apply regardless of the 100 ft distance to the main panel.

Subpanel installations at detached structures

100 ft feeder circuits to detached structures typically include subpanel installations at the destination. Detached structures require ground rod installation at the subpanel per NEC 250.32. The 4-wire feeder requirement (2 hots, neutral, ground) applies for all new subpanel installations since 2008 NEC.

Main panel breaker sizing

The main panel breaker size for a 100 ft feeder circuit must match both the feeder wire ampacity and the downstream subpanel or load requirements. For a 60A garage subpanel feeder at 100 ft using 6 AWG copper, use a 60 amp breaker at the main panel. For a 100A garage subpanel feeder at 100 ft using 3 AWG copper, use a 100 amp breaker at the main panel.

Grounding electrode requirements

Detached structures fed by 100 ft feeders require grounding electrode installation per NEC 250.32. Typically a single 8 foot copper-clad ground rod at the detached structure with grounding electrode conductor sized per NEC 250.66 based on the ungrounded (hot) feeder conductor size. For 6 AWG copper feeder, minimum grounding electrode conductor is 8 AWG copper.

5 Common Mistakes When Sizing Wire for 100 ft Runs

The mistakes below cause the most frequent buyer questions about wire size for 100 ft run installations.

Mistake 1: Using ampacity-minimum wire without voltage drop verification

The most common mistake at 100 ft is selecting wire based only on ampacity requirements without calculating voltage drop. A 30 amp circuit that uses 10 AWG copper for short runs (ampacity minimum) needs upgrade to 8 AWG copper at 100 ft due to voltage drop. Always verify voltage drop calculation for runs over 50 feet using our voltage drop calculator.

Mistake 2: Applying 240V wire sizes to 120V circuits

Some installers use 240V wire size tables for 120V circuits, resulting in undersized wire and excessive voltage drop. At 100 ft, 120V circuits typically need wire one to two sizes larger than 240V equivalents because voltage drop as a percentage is twice as bad at 120V. A 15 amp 120V circuit at 100 ft needs 8 AWG copper rather than the 14 AWG that would seem adequate based on 240V thinking.

Mistake 3: Ignoring continuous load duration

For continuous loads at 100 ft (EV chargers, water heaters, HVAC equipment operating for extended periods), size the wire for the continuous current with the appropriate NEC continuous load factor (typically 125 percent). A 48 amp EV charger circuit at 100 ft requires wire sized for 60 amp continuous per NEC 625.42, not just the 48 amp charging current.

Mistake 4: Forgetting motor starting inrush for motor circuits

Motor circuits at 100 ft (well pumps, HVAC compressors, air compressors) draw 4-8 times running current during starting. Voltage drop during starting can exceed 15-20 percent even when running voltage drop is well under 3 percent. Size motor circuits for adequate starting voltage as well as running voltage. Well pumps in particular need extra care at 100 ft due to their high inrush current.

Mistake 5: Not accounting for total feeder plus branch drop

For 100 ft feeder circuits to subpanels with additional branch circuits at the subpanel, both segments contribute to total voltage drop. If the feeder has 3 percent drop and branch circuits add another 3 percent, total drop is 6 percent which exceeds the NEC 5 percent combined limit. Plan feeder and branch circuits together to keep combined drop under 5 percent.

Conclusion

The wire size for 100 ft run varies based on load current, voltage, and conductor material. At 240V single-phase with copper conductors and 3 percent maximum voltage drop, common wire sizes at 100 ft are 12 AWG for 15A, 10 AWG for 20A, 8 AWG for 30-40A, 6 AWG for 50-60A, 4 AWG for 80A, 3 AWG for 100-125A, 2 AWG for 150A, and 1 AWG for 200A. At 120V, wire sizes are typically one to two sizes larger due to worse voltage drop percentage.

100 ft is the critical distance threshold where voltage drop typically becomes the limiting factor for wire size selection rather than ampacity alone. Both ampacity per NEC Table 310.16 and voltage drop per NEC 210.19 and 215.2 informational notes must be satisfied for good installation performance. Verify wire size using the reference tables in this article, our quick lookup widget, or the interactive voltage drop calculator for wire that provides real-time calculation with pass/fail indicators against the NEC 3 percent recommendation.

This article was last reviewed and updated in June 2026 to reflect current National Electrical Code recommendations and wire sizing methodology at 100 ft distance. Wire sizing recommendations are based on the current NEC (NFPA 70) and should be verified against specific installation conditions and local code amendments. For critical installations or unusual conditions, use our voltage drop calculator or consult a licensed electrician. NEC voltage drop recommendations are in informational notes rather than mandatory code requirements.