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Wire Gauge & Ampacity Calculator (AWG)

Find the right AWG wire for your current and voltage drop. Includes ampacity lookup and mm² cross-reference.

MODE:
A
Result
AWG 0
smallest gauge that handles 5 A (chassis wiring)
Diameter
8.251 mm
Cross-section
53.475 mm²
Ampacity (chassis)
245 A
Use AWG 0 wire for 5 A — connect it to a PCB in the editor →
Method & assumptions

AWG → diameter: d(mm) = 0.127 × 92(36−n)/39.

Ampacity table is for chassis wiring (single insulated conductor in free air). For wires bundled inside conduit or a harness, derate by 20–40% depending on bundle size. Values follow the widely-cited chassis-wiring table (roughly aligned with NEC single-conductor free-air data at 60 °C insulation rating).

What size wire for 40 amp?

AWG 8 wire handles about 73 A chassis-rated. For 40 A continuous, AWG 8 is the safe pick with headroom; AWG 10 is marginal at 55 A. Always verify against your local code (NEC for the US) if this is mains wiring.

How many amps can 18-gauge wire handle?

AWG 18 handles about 16 A chassis-rated. For power-tool cords or continuous loads, treat this as an upper limit with margin; typical hookup use is 5–10 A.

What gauge wire for 50 amp?

AWG 6 (~101 A chassis) is the standard choice for 50 A continuous. AWG 8 (~73 A) is enough for chassis wiring but leaves less margin for temperature or bundling derating.

Frequently asked

What size wire for 40 amp?
AWG 8 handles ~73 A chassis, giving comfortable headroom for 40 A. AWG 10 at ~55 A is marginal.
How many amps can 18-gauge wire handle?
AWG 18 handles about 16 A in free-air chassis wiring. In bundles or higher ambient temperatures, derate to 10–12 A.
What gauge wire for 50 amp?
AWG 6 (~101 A chassis) is the standard pick. AWG 8 (~73 A) works with less margin.
How to determine wire gauge?
Start from your maximum continuous current. Add margin for temperature and bundling. Pick the smallest AWG whose ampacity exceeds that number. This calculator does it directly.
Next step

Bringing those wires onto a board? Put the screw terminal or header you need into the description and PCBEditor places it with the rest of the circuit.

Connect wires to a PCB in the editor →
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