8 AWG at 60A and 150 Feet: Ampacity-Invalid Reference Calculation

Reference voltage-drop calculation only. 8 AWG is NEC-capped at 50A branch-circuit OCP per NEC 240.4(D) (75°C ampacity 50A), so 60A on this gauge fails the ampacity check before voltage drop ever enters the conversation. Do not use the number below as an install spec. As a load-side reference, 8 AWG copper at 60 amps over 150 feet on a single-phase / DC circuit would drop 14 volts (11.67% on 120V, 5.84% on 240V).

8 AWG, 60A, 150ft · single-phase / DC · reference only, ampacity-invalid

14 V drop (11.67% on 120V)

On 120V circuit11.67%

On 240V circuit5.84%

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

8 AWG

Amps

Feet

Drop @ 120V

14.00V (11.67%)

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 × 150 × 60 × 0.778) ÷ 1000 = 14 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: (14 ÷ 120) × 100 = 11.67%

On 240V: (14 ÷ 240) × 100 = 5.84%

How This Estimate Changes with Run Length and Gauge

Gauge That Meets the 3% Target

8 AWG can't carry the 60A load in the first place, its branch-circuit OCP cap is 50A under typical conditions. The smallest gauge in our table that clears both the ampacity cap and the 3% drop target at these inputs is 2 AWG. Run the full wire-size calculator for run length, material, and drop-target variations.

Impact of Distance

Voltage drop is proportional to distance. Here is 8 AWG at 60A at different distances:

Distance	Drop (V)	% on 120V	% on 240V	NEC (120V)
25ft	2.33V	1.95%	0.9725%	OK
50ft	4.67V	3.89%	1.95%	Caution
75ft	7V	5.84%	2.92%	Past 5%
100ft	9.34V	7.78%	3.89%	Past 5%
150ft	14V	11.67%	5.84%	Past 5%
200ft	18.67V	15.56%	7.78%	Past 5%
300ft	28.01V	23.34%	11.67%	Past 5%

Same Run, Different Wire Gauges

How does wire gauge affect voltage drop for 60A at 150 feet on 120V single-phase / DC? Only gauges whose branch-circuit OCP cap is at or above the 60A 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	8.84V	7.36%	3.68%	Past 5%
4 AWG	5.54V	4.62%	2.31%	Caution
3 AWG	4.41V	3.68%	1.84%	Caution
2 AWG	3.49V	2.91%	1.46%	OK
1 AWG	2.77V	2.31%	1.16%	OK
1/0 AWG	2.2V	1.83%	0.915%	OK
2/0 AWG	1.74V	1.45%	0.7253%	OK
3/0 AWG	1.38V	1.15%	0.5745%	OK
4/0 AWG	1.09V	0.912%	0.456%	OK
250 kcmil	0.927V	0.7725%	0.3863%	OK
300 kcmil	0.7722V	0.6435%	0.3218%	OK
350 kcmil	0.6606V	0.5505%	0.2753%	OK
500 kcmil	0.4644V	0.387%	0.1935%	OK
750 kcmil	0.3078V	0.2565%	0.1283%	OK

Related Calculations

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Frequently Asked Questions

What is the voltage drop for 8 AWG at 60A and 150ft?expand_more

8 AWG carrying 60A over 150ft has a 14V drop (11.67% on 120V), but 8 AWG is NEC-capped at 50A branch-circuit OCP per NEC 240.4(D), so 60A on 8 AWG is ampacity-invalid and the drop figure above is a reference calculation only, not an install spec. Reference: 5.84% on 240V.

Does 8 AWG meet the 3% drop target at 60A and 150ft on 120V?expand_more

On 120V, this run sits at 11.67%, which is past both 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. However, 8 AWG is ampacity-invalid for 60A (NEC 240.4(D) caps 8 AWG at 50A branch-circuit OCP), so this is a reference drop calculation only and the 3% check does not make this a valid install.

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 5.84% on 240V versus 11.67% on 120V.

How do I reduce voltage drop?expand_more

Use a larger wire gauge (lower AWG number), shorten the run, or increase the source voltage. Each option reduces the percentage drop, and higher source voltage is usually the most effective change for long runs because the drop is a smaller fraction of a larger reference.

Does wire material affect voltage drop?expand_more

Yes. Aluminum has roughly 1.3 to 1.4 times the resistance of copper at the NEC Chapter 9 Table 8 75°C reference temperature, so for the same voltage drop an aluminum conductor is typically one to two gauges larger than copper. The exact gap depends on whether ampacity or voltage drop is binding, and the install still needs anti-oxidant compound and aluminum-rated lugs.

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.