Wire Sizing

Wire Size for Hot Tub — 50 Amp 100 Feet

Pre-calculated NEC-compliant wire size for 50 amps at 100 feet on a 240V single-phase circuit. Immediate answer below.

Recommended Wire Size

Copper

6 AWG

Voltage drop: 2.05% (4.91V)

Voltage at load: 235.1V

Controlling factor: Voltage Drop (3% limit)

Aluminum

4 AWG

Voltage drop: 2.12% (5.08V)

Voltage at load: 234.9V

Controlling factor: Voltage Drop (3% limit)

Based on NEC Table 310.16 (75°C column), single-phase, 240V, 3% max voltage drop, one-way distance 100 ft.

Wire Comparison Table

Wire Size	Ampacity	V-Drop (V)	V-Drop (%)	V at Load
14 AWG	15A	31.4V	13.08%	208.6V
12 AWG	20A	19.8V	8.25%	220.2V
10 AWG	30A	12.4V	5.17%	227.6V
8 AWG	50A	7.78V	3.24%	232.2V
6 AWGREC	65A	4.91V	2.05%	235.1V
4 AWG	85A	3.08V	1.28%	236.9V
3 AWG	100A	2.45V	1.02%	237.6V
2 AWG	115A	1.94V	0.81%	238.1V
1 AWG	130A	1.54V	0.64%	238.5V
1/0 AWG	150A	1.22V	0.51%	238.8V
2/0 AWG	175A	0.97V	0.4%	239V
3/0 AWG	200A	0.77V	0.32%	239.2V
4/0 AWG	230A	0.61V	0.25%	239.4V
250 kcmil	255A	0.52V	0.21%	239.5V
300 kcmil	285A	0.43V	0.18%	239.6V
350 kcmil	310A	0.37V	0.15%	239.6V
400 kcmil	335A	0.32V	0.13%	239.7V
500 kcmil	380A	0.26V	0.11%	239.7V

Table shows all standard AWG/kcmil sizes for 50A at 100 ft on 240V (copper). Green check = meets both ampacity and 3% voltage drop. REC = smallest compliant size.

Key Considerations

For a 50A circuit at 100 feet on 240V, both ampacity and voltage drop must be satisfied. NEC recommends keeping the total voltage drop (feeder + branch) under 5%, with no more than 3% on either segment alone.

Copper conductors at 75°C column (THHN/THWN-2) are assumed. If using 60°C terminations, derate the ampacity to the 60°C column values. Verify the temperature rating of your terminals.

Frequently Asked Questions

What size wire do I need for a 50 amp service at 100 feet?▾

For a 50A/240V circuit at 100 feet, use 6 AWG copper (2.05% drop) or 4 AWG aluminum. This keeps voltage drop within the NEC-recommended 3% limit.

Can I use aluminum wire for a 50 amp circuit?▾

Yes. Aluminum wire is a cost-effective alternative for larger circuits. For 50A at 100 feet, use 4 AWG aluminum (2.12% voltage drop). Aluminum requires AL-rated connectors and anti-oxidant compound at all terminations.

What happens if the voltage drop exceeds 3%?▾

Voltage drop above 3% reduces equipment efficiency, can cause motors to overheat, and may violate NEC 210.19(A) Informational Note No. 4. For a 50A circuit at 100 feet on 240V, exceeding 3% means the load receives less than 232.8V, which can damage sensitive electronics and shorten appliance lifespan.

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Different voltage, three-phase, or custom max drop percentage? Use our interactive calculator.

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