220V Wire Gauge Size Calculator

220V Wire Gauge Sizing

220 V circuits power dryers, welders, heat pumps, and shop equipment. Wire must carry the load current safely (NEC ampacity) and keep voltage drop reasonable over the feeder length.

Ampacity Plus Voltage Drop

Select the smallest conductor where:

$$\text{Ampacity} \geq I \quad \text{and} \quad \%\text{drop} \leq \%\text{drop}_{\max}$$

Single-phase AC drop:

$$V_{\text{drop}} = 2 \times I \times R \times L$$

Three-phase AC drop:

$$V_{\text{drop}} = \sqrt{3} \times I \times R \times L$$

Frequently Asked Questions

What wire for a 30 amp 220V circuit?

10 AWG copper meets the 35 A ampacity rating. On a 75 ft run at 30 A, 10 AWG usually keeps drop under 3%. Longer runs may need 8 AWG.

Is 220V single-phase or two hot legs?

Residential 220 V is typically single-phase with two ungrounded conductors. Use single-phase mode unless you have a true three-phase supply.

What max voltage drop should I use?

NEC suggests 5% total from service to outlet. Many designers use 3% on the branch circuit portion. This tool defaults to 3%.

Copper vs aluminum at 220V?

Copper fits in smaller conduit and has lower drop. Aluminum is lighter and cheaper but needs larger gauge and listed connectors.

Does temperature rating change ampacity?

Yes. This tool uses NEC 75°C column values. Higher insulation ratings allow more current; verify with your local authority.

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220V Wire Size Calculator

220V Wire Gauge Sizing

Ampacity Plus Voltage Drop

Frequently Asked Questions

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