What Is the Voltage Drop for 6 AWG at 17A and 100 Feet?

6 AWG copper carrying 17 amps over 100 feet on a single-phase / DC circuit drops 1.67 volts (1.39% 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.

6 AWG, 17A, 100ft · single-phase / DC

1.67 V drop (1.39% on 120V)

On 120V circuit1.39%

On 240V circuit0.6956%

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

6 AWG

Amps

Feet

Drop @ 120V

1.67V (1.39%)

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 × 17 × 0.491) ÷ 1000 = 1.67 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: (1.67 ÷ 120) × 100 = 1.39%

On 240V: (1.67 ÷ 240) × 100 = 0.6956%

How This Estimate Changes with Run Length and Gauge

Gauge Check

6 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 6 AWG at 17A at different distances:

Distance	Drop (V)	% on 120V	% on 240V	NEC (120V)
25ft	0.4173V	0.3478%	0.1739%	OK
50ft	0.8347V	0.6956%	0.3478%	OK
75ft	1.25V	1.04%	0.5217%	OK
100ft	1.67V	1.39%	0.6956%	OK
150ft	2.5V	2.09%	1.04%	OK
200ft	3.34V	2.78%	1.39%	OK
300ft	5.01V	4.17%	2.09%	Caution

Same Run, Different Wire Gauges

How does wire gauge affect voltage drop for 17A at 100 feet on 120V single-phase / DC? Only gauges whose branch-circuit OCP cap is at or above the 17A 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)
6 AWG	1.67V	1.39%	0.6956%	OK
4 AWG	1.05V	0.8727%	0.4363%	OK
3 AWG	0.833V	0.6942%	0.3471%	OK
2 AWG	0.6596V	0.5497%	0.2748%	OK
1 AWG	0.5236V	0.4363%	0.2182%	OK
1/0 AWG	0.4148V	0.3457%	0.1728%	OK

Related Calculations

cable Wire size: 17A, 100ft bolt Watts to amps calculator functions Voltage drop formula

Frequently Asked Questions

What is the voltage drop for 6 AWG at 17A and 100ft?expand_more

6 AWG carrying 17A over 100ft has a 1.67V drop (1.39% on 120V). Reference: 0.6956% 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 6 AWG meet the 3% drop target at 17A and 100ft on 120V?expand_more

On 120V, this run sits at 1.39%, 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 6 AWG for this run?expand_more

6 AWG already sits within the 3% branch-circuit drop target at these inputs (1.39% 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 0.6956% on 240V versus 1.39% 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.