What Is the Voltage Drop for 4/0 AWG at 26A and 100 Feet?

4/0 AWG copper carrying 26 amps over 100 feet on a single-phase / DC circuit drops 0.3162 volts (0.2635% on a 120V source). This sits within the 3% branch target and the 5% feeder+branch total target that NEC 210.19(A) Informational Note 4 cites. Both are planning targets, not code requirements.

4/0 AWG, 26A, 100ft · single-phase / DC

0.3162 V drop (0.2635% on 120V)

On 120V circuit0.2635%

On 240V circuit0.1317%

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

4/0 AWG

Amps

Feet

Drop @ 120V

0.32V (0.26%)

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 × 100 × 26 × 0.0608) ÷ 1000 = 0.3162 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: (0.3162 ÷ 120) × 100 = 0.2635%

On 240V: (0.3162 ÷ 240) × 100 = 0.1317%

How This Estimate Changes with Run Length and Gauge

Gauge Check

4/0 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 4/0 AWG at 26A at different distances:

Distance	Drop (V)	% on 120V	% on 240V	NEC (120V)
25ft	0.079V	0.0659%	0.0329%	OK
50ft	0.1581V	0.1317%	0.0659%	OK
75ft	0.2371V	0.1976%	0.0988%	OK
100ft	0.3162V	0.2635%	0.1317%	OK
150ft	0.4742V	0.3952%	0.1976%	OK
200ft	0.6323V	0.5269%	0.2635%	OK
300ft	0.9485V	0.7904%	0.3952%	OK

Same Run, Different Wire Gauges

How does wire gauge affect voltage drop for 26A at 100 feet on 120V single-phase / DC? Only gauges whose branch-circuit OCP cap is at or above the 26A 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)
4/0 AWG	0.3162V	0.2635%	0.1317%	OK
250 kcmil	0.2678V	0.2232%	0.1116%	OK
300 kcmil	0.2231V	0.1859%	0.093%	OK
350 kcmil	0.1908V	0.159%	0.0795%	OK
500 kcmil	0.1342V	0.1118%	0.0559%	OK
750 kcmil	0.0889V	0.0741%	0.0371%	OK

Related Calculations

cable Wire size: 26A, 100ft bolt Watts to amps calculator functions Voltage drop formula

Frequently Asked Questions

What is the voltage drop for 4/0 AWG at 26A and 100ft?expand_more

4/0 AWG carrying 26A over 100ft has a 0.3162V drop (0.2635% on 120V). Reference: 0.1317% 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 4/0 AWG meet the 3% drop target at 26A and 100ft on 120V?expand_more

On 120V, this run sits at 0.2635%, 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.

What wire gauge should I use instead of 4/0 AWG for this run?expand_more

4/0 AWG already sits within the 3% branch-circuit drop target at these inputs (0.2635% 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.

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 0.1317% on 240V versus 0.2635% on 120V.

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.