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Calculator

Wire Gauge & Current Calculator

Pick the right AWG wire size: current rating, resistance and voltage drop.

A
m
V

Result

Voltage drop (round trip)
0.212 V (1.77 %)
Max current — chassis wiring
7 A
Max current — power transmission
0.918 A
Diameter
0.644 mm
Cross-section
0.326 mm²
Resistance
53 mΩ/m
Power lost as heat
212 mW
  • !Fine for short wiring inside equipment, but too high for bundled or long power runs.
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How it works

Thin wire is easy to route but it heats up and drops voltage when carrying too much current. Thick wire is safe but bulky. This calculator shows the key numbers for each American Wire Gauge (AWG) size and how much voltage you will lose over a given length.

Ampacity figures are conservative guides. 'Chassis wiring' assumes short runs inside equipment with decent airflow; 'power transmission' is the stricter figure for bundled or long runs (about 700 circular mils per amp). Voltage drop is computed for the round trip (out and back) of solid copper at 20 °C.

Formula

Diameterd(mm) = 0.127 × 92^((36 − AWG) / 39)
ResistanceR = ρ × L / A (ρ(copper) ≈ 1.72 × 10⁻⁸ Ω·m)
Voltage dropVdrop = I × R(round trip) = I × R/m × 2 × length

Worked example. 24 AWG wire carrying 1 A over 2 m (4 m round trip): R = 0.084 Ω/m × 4 m = 0.34 Ω, so the drop is 0.34 V — about 2.8% on a 12 V supply.

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Frequently asked questions

What wire gauge should I use for breadboard jumpers?

22–26 AWG solid core is typical for breadboards. For anything carrying more than about 1 A, use thicker stranded wire such as 20 or 18 AWG.

What gauge for a 5 V / 2 A Raspberry Pi or ESP32 supply?

Use at least 22 AWG for short runs and 20 AWG if the cable is longer than 1–2 m. At 5 V, even 0.25 V of drop is 5% — which can trigger brown-outs.

Does a lower AWG number mean thicker wire?

Yes. Smaller AWG numbers are thicker wire. Every 3 gauge steps roughly doubles the cross-section area and halves the resistance.

Is stranded or solid wire better?

Solid wire suits breadboards and permanent connections. Stranded wire flexes without breaking, so it is better for anything that moves. Resistance is slightly higher in stranded wire of the same gauge.

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