6 AWG at 80A and 150 Feet: Ampacity-Invalid Reference Calculation

Reference voltage-drop calculation only. 6 AWG is NEC-capped at 65A branch-circuit OCP per NEC 240.4(D) (75°C ampacity 65A), so 80A on this gauge fails the ampacity check before voltage drop ever enters the conversation. Do not use the number below as an install spec. The reference math on the single-phase / DC basis gives a 11.78-volt drop (9.82% on 120V). For an install at 80A, start with a conductor whose NEC 240.4(D) branch-circuit OCP cap is at or above 80A, then check voltage drop against that gauge.

6 AWG, 80A, 150ft · single-phase / DC · reference only, ampacity-invalid

11.78 V drop (9.82% on 120V)

On 120V circuit9.82%

On 240V circuit4.91%

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

11.78V (9.82%)

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 × 80 × 0.491) ÷ 1000 = 11.78 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: (11.78 ÷ 120) × 100 = 9.82%

On 240V: (11.78 ÷ 240) × 100 = 4.91%

How This Estimate Changes with Run Length and Gauge

Gauge That Meets the 3% Target

6 AWG can't carry the 80A load in the first place, its branch-circuit OCP cap is 65A under typical conditions. The smallest gauge in our table that clears both the ampacity cap and the 3% drop target at these inputs is 1/0 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 6 AWG at 80A at different distances:

Distance	Drop (V)	% on 120V	% on 240V	NEC (120V)
25ft	1.96V	1.64%	0.8183%	OK
50ft	3.93V	3.27%	1.64%	Caution
75ft	5.89V	4.91%	2.46%	Caution
100ft	7.86V	6.55%	3.27%	Past 5%
150ft	11.78V	9.82%	4.91%	Past 5%
200ft	15.71V	13.09%	6.55%	Past 5%
300ft	23.57V	19.64%	9.82%	Past 5%

Same Run, Different Wire Gauges

How does wire gauge affect voltage drop for 80A at 150 feet on 120V single-phase / DC? Only gauges whose branch-circuit OCP cap is at or above the 80A 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	7.39V	6.16%	3.08%	Past 5%
3 AWG	5.88V	4.9%	2.45%	Caution
2 AWG	4.66V	3.88%	1.94%	Caution
1 AWG	3.7V	3.08%	1.54%	Caution
1/0 AWG	2.93V	2.44%	1.22%	OK
2/0 AWG	2.32V	1.93%	0.967%	OK
3/0 AWG	1.84V	1.53%	0.766%	OK
4/0 AWG	1.46V	1.22%	0.608%	OK
250 kcmil	1.24V	1.03%	0.515%	OK
300 kcmil	1.03V	0.858%	0.429%	OK
350 kcmil	0.8808V	0.734%	0.367%	OK
500 kcmil	0.6192V	0.516%	0.258%	OK
750 kcmil	0.4104V	0.342%	0.171%	OK

Related Calculations

cable Wire size: 80A, 150ft bolt Watts to amps calculator functions Voltage drop formula

Frequently Asked Questions

What is the voltage drop for 6 AWG at 80A and 150ft?expand_more

6 AWG carrying 80A over 150ft has an 11.78V drop (9.82% on 120V), but 6 AWG is NEC-capped at 65A branch-circuit OCP per NEC 240.4(D), so 80A on 6 AWG is ampacity-invalid and the drop figure above is a reference calculation only, not an install spec. Reference: 4.91% 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.

What wire gauge should I use instead of 6 AWG for this run?expand_more

This run is at 9.82% on 120V, past the 3% branch-circuit drop target. If you want to land under 3% at 80A over 150ft on 120V, the smallest gauge in our table that clears it is 1/0 AWG at 2.44%. Going up one size from 6 AWG is not always enough, each AWG step only drops the resistance by roughly 20-25%, so on long runs or high currents you often have to skip one or two sizes to meet the target. NEC 210.19(A) Informational Note 4 frames 3% as a recommendation, not a code requirement, so the right answer for you also depends on the load (motor startup, sensitive electronics) and how much drop is tolerable.

What happens if voltage drop is too high?expand_more

Motors run hotter and can have trouble starting under load. Incandescent and halogen lighting dims. Some electronics misbehave at the low end of their input tolerance. Energy is wasted as I²R heating in the conductor. These are performance issues; high drop is not itself a code violation unless the specific installation cites a hard limit.

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.