What Is the Voltage Drop for 1 AWG at 104A and 50 Feet?

Running 104A through 1 AWG copper for 50 feet on a single-phase / DC circuit produces a 1.6-volt drop. On a 120V source that is 1.33%; on 240V it is 0.6673%. 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.

1 AWG, 104A, 50ft · single-phase / DC

1.6 V drop (1.33% on 120V)

On 120V circuit1.33%

On 240V circuit0.6673%

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

1 AWG

Amps

Feet

Drop @ 120V

1.60V (1.33%)

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 × 50 × 104 × 0.154) ÷ 1000 = 1.6 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: (1.6 ÷ 120) × 100 = 1.33%

On 240V: (1.6 ÷ 240) × 100 = 0.6673%

How This Estimate Changes with Run Length and Gauge

Gauge Check

1 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 1 AWG at 104A at different distances:

Distance	Drop (V)	% on 120V	% on 240V	NEC (120V)
25ft	0.8008V	0.6673%	0.3337%	OK
50ft	1.6V	1.33%	0.6673%	OK
75ft	2.4V	2%	1%	OK
100ft	3.2V	2.67%	1.33%	OK
150ft	4.8V	4%	2%	Caution
200ft	6.41V	5.34%	2.67%	Past 5%
300ft	9.61V	8.01%	4%	Past 5%

Same Run, Different Wire Gauges

How does wire gauge affect voltage drop for 104A at 50 feet on 120V single-phase / DC? Only gauges whose branch-circuit OCP cap is at or above the 104A 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)
1 AWG	1.6V	1.33%	0.6673%	OK
1/0 AWG	1.27V	1.06%	0.5287%	OK
2/0 AWG	1.01V	0.8381%	0.419%	OK
3/0 AWG	0.7966V	0.6639%	0.3319%	OK
4/0 AWG	0.6323V	0.5269%	0.2635%	OK
250 kcmil	0.5356V	0.4463%	0.2232%	OK

Related Calculations

cable Wire size: 104A, 50ft bolt Watts to amps calculator functions Voltage drop formula

Frequently Asked Questions

What is the voltage drop for 1 AWG at 104A and 50ft?expand_more

1 AWG carrying 104A over 50ft has a 1.6V drop (1.33% on 120V). Reference: 0.6673% on 240V.

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 0.6673% on 240V versus 1.33% on 120V.

What wire gauge should I use instead of 1 AWG for this run?expand_more

1 AWG already sits within the 3% branch-circuit drop target at these inputs (1.33% 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.

Does 1 AWG meet the 3% drop target at 104A and 50ft on 120V?expand_more

On 120V, this run sits at 1.33%, 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.

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.

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.