Wire gauge & voltage drop calculator
Pick the right copper wire for a low-voltage project. Convert AWG to mm², see the wire's resistance and voltage drop over your cable length, and get a cautious current guide. For learning and hobby circuits only, not mains wiring.
Enter your values
How thick should your wire be? See size, resistance and a careful current guide for AWG and metric (mm²) copper wire.
AWG table (copper, 20 °C)
| Size | Ø mm | mm² | Ω/km | Guide A |
|---|
Result
Educational guide only. The current figures are deliberately cautious, for low-voltage hobby projects. They are not for mains wiring. For anything connected to the mains, follow your local electrical code and use a qualified electrician.
AWG Ø = 0.127 mm × 92(36 − n)/39R = ρ ÷ A = 17.24 ÷ A(mm²) Ω/kmGuide current = circular mils ÷ 700Voltage drop = I × R × 2LCoro's tip: Thin wire acts like a small resistor. It wastes voltage and gets warm. If your motor or LED strip is weak at the far end, check the voltage drop first.
Wire gauge & voltage drop calculator: common questions
How do I convert AWG to mm²?
The AWG diameter is 0.127 mm × 92^((36 − n) ÷ 39); area = π × d² ÷ 4. For example 22 AWG ≈ 0.33 mm² and 18 AWG ≈ 0.82 mm².
How do I calculate voltage drop in a wire?
Voltage drop = current × wire resistance × 2 × length (out and back). Copper is about 17.24 ÷ area(mm²) ohms per kilometre at 20 °C.
Can I use this for house wiring?
No. The current guide here is for low-voltage hobby projects. For mains wiring, follow your local electrical code and use a qualified electrician.
For learning and low-voltage hobby circuits (12 V and below). Always check the part's datasheet. Never use these tools to plan mains (230 V) wiring.