What Is the Voltage Drop for 4 AWG at 11A and 125 Feet?

Running 11A through 4 AWG copper for 125 feet on a single-phase / DC circuit produces a 0.847-volt drop. On a 120V source that is 0.7058%; on 240V it is 0.3529%. NEC 210.19(A) Informational Note 4 recommends keeping branch-circuit drop at or below 3% and total feeder+branch drop at or below 5%, these are performance recommendations, not code requirements.

4 AWG, 11A, 125ft · single-phase / DC

0.847 V drop (0.7058% on 120V)

On 120V circuit0.7058%

On 240V circuit0.3529%

Circuit basis: This uses the single-phase / DC round-trip formula (factor of 2) for the voltage drop across the two circuit conductors. For a three-phase line-to-line run use the three-phase version of the page (append ?type=3ph). Switch to the three-phase version →

Gauge

4 AWG

Amps

Feet

Drop @ 120V

0.85V (0.71%)

Assumes a 120V source on a single-phase / DC circuit. Use the circuit-basis link above to switch between single-phase/DC and three-phase.

Voltage Drop Formula (single-phase / DC)

V_drop = (2 × L × I × R) ÷ 1000

(2 × 125 × 11 × 0.308) ÷ 1000 = 0.847 V

DC and single-phase AC use the round-trip factor of 2. Current travels out to the load on one conductor and returns on another.

For a three-phase circuit at the same amps and distance, see the three-phase version (uses √3 instead of 2, so the drop is about 13.4% lower).

Percentage

%VD = (V_drop ÷ V_source) × 100

On 120V: (0.847 ÷ 120) × 100 = 0.7058%

On 240V: (0.847 ÷ 240) × 100 = 0.3529%

How This Estimate Changes with Run Length and Gauge

Gauge Check

4 AWG clears the 3% drop target at these inputs. A smaller conductor may also meet it with less margin. See the minimum gauge for this load and distance.

Impact of Distance

Voltage drop is proportional to distance. Here is 4 AWG at 11A at different distances:

Distance	Drop (V)	% on 120V	% on 240V	NEC (120V)
25ft	0.1694V	0.1412%	0.0706%	OK
50ft	0.3388V	0.2823%	0.1412%	OK
75ft	0.5082V	0.4235%	0.2118%	OK
100ft	0.6776V	0.5647%	0.2823%	OK
150ft	1.02V	0.847%	0.4235%	OK
200ft	1.36V	1.13%	0.5647%	OK
300ft	2.03V	1.69%	0.847%	OK

Same Run, Different Wire Gauges

How does wire gauge affect voltage drop for 11A at 125 feet on 120V single-phase / DC? Only gauges whose branch-circuit OCP cap is at or above the 11A load are listed, since thinner gauges would fail the ampacity check before drop even matters.

Gauge	Drop (V)	% on 120V	% on 240V	3% Target (120V)
4 AWG	0.847V	0.7058%	0.3529%	OK
3 AWG	0.6738V	0.5615%	0.2807%	OK
2 AWG	0.5335V	0.4446%	0.2223%	OK
1 AWG	0.4235V	0.3529%	0.1765%	OK
1/0 AWG	0.3355V	0.2796%	0.1398%	OK
2/0 AWG	0.2659V	0.2216%	0.1108%	OK

Related Calculations

cable Wire size: 11A, 125ft bolt Watts to amps calculator functions Voltage drop formula

Frequently Asked Questions

What is the voltage drop for 4 AWG at 11A and 125ft?expand_more

4 AWG carrying 11A over 125ft has a 0.847V drop (0.7058% on 120V). Reference: 0.3529% on 240V.

Why does distance affect voltage drop?expand_more

Voltage drop is proportional to distance. The formula multiplies by 2 × the distance (out and back). Doubling the run doubles the drop.

Does 4 AWG meet the 3% drop target at 11A and 125ft on 120V?expand_more

On 120V, this run sits at 0.7058%, which is within the 3% branch and 5% feeder+branch total drop targets. NEC 210.19(A) Informational Note 4 cites 3% for branch circuits and 5% for total feeder+branch drop as performance recommendations, not hard code requirements.

Is voltage drop worse on 120V or 240V?expand_more

Same wire, same amps, same distance: the volts dropped are identical. But the percentage is worse on 120V because the drop is a larger fraction of the source voltage. This run would be 0.3529% on 240V versus 0.7058% on 120V.

What wire gauge should I use instead of 4 AWG for this run?expand_more

4 AWG already sits within the 3% branch-circuit drop target at these inputs (0.7058% on 120V). Going to a larger gauge is only useful if you want more headroom for future load growth, longer runs, or tighter drop targets like the 5% feeder+branch total recommendation used in sensitive or motor-heavy installations.

This calculator provides estimates for reference purposes only. Always consult a licensed electrician and verify compliance with the National Electrical Code (NEC) and local electrical codes before performing any electrical work.