6 AWG at 80A and 50 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 3.93-volt reference drop at 80A through 6 AWG for 50 feet is still a valid I×R calculation across the conductor, which is why this page renders it, but it is a reference-only figure and not a permission slip to run that current on that gauge.

6 AWG, 80A, 50ft · single-phase / DC · reference only, ampacity-invalid

3.93 V drop (3.27% on 120V)

On 120V circuit3.27%

On 240V circuit1.64%

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

3.93V (3.27%)

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 × 80 × 0.491) ÷ 1000 = 3.93 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: (3.93 ÷ 120) × 100 = 3.27%

On 240V: (3.93 ÷ 240) × 100 = 1.64%

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 4 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 50 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	2.46V	2.05%	1.03%	OK
3 AWG	1.96V	1.63%	0.8167%	OK
2 AWG	1.55V	1.29%	0.6467%	OK
1 AWG	1.23V	1.03%	0.5133%	OK
1/0 AWG	0.976V	0.8133%	0.4067%	OK
2/0 AWG	0.7736V	0.6447%	0.3223%	OK
3/0 AWG	0.6128V	0.5107%	0.2553%	OK
4/0 AWG	0.4864V	0.4053%	0.2027%	OK
250 kcmil	0.412V	0.3433%	0.1717%	OK
300 kcmil	0.3432V	0.286%	0.143%	OK
350 kcmil	0.2936V	0.2447%	0.1223%	OK
500 kcmil	0.2064V	0.172%	0.086%	OK
750 kcmil	0.1368V	0.114%	0.057%	OK

Related Calculations

cable Wire size: 80A, 50ft bolt Watts to amps calculator functions Voltage drop formula

Frequently Asked Questions

What is the voltage drop for 6 AWG at 80A and 50ft?expand_more

6 AWG carrying 80A over 50ft has a 3.93V drop (3.27% 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: 1.64% on 240V.

Does 6 AWG meet the 3% drop target at 80A and 50ft on 120V?expand_more

On 120V, this run sits at 3.27%, which is past the 3% branch target; within the 5% feeder+branch total. 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, 6 AWG is ampacity-invalid for 80A (NEC 240.4(D) caps 6 AWG at 65A branch-circuit OCP), so this is a reference drop calculation only and the 3% check does not make this a valid install.

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.

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.

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.