Wire Gauge Calculator
Work out the wire gauge needed to carry a current safely over a distance.
Sizing wire for the current
Wire has to be thick enough to carry its current without overheating, and thin wire carrying too much current is a genuine fire risk. This helps work out the gauge needed from the current and the run length, an important safety calculation for any wiring job.
Enter the current and distance to see the suitable gauge.
Current, heat and voltage drop
Two things drive wire sizing. The first is heat: too much current in too thin a wire makes it hot, which is dangerous, so there are rated limits for how much current each gauge can safely carry. The second is voltage drop: over a long run, thin wire loses voltage along the way, so a distant load may not get enough — which is why long runs need thicker wire than the current alone would suggest. Gauge numbering is also counterintuitive, with smaller numbers meaning thicker wire.
Questions & answers
Why does a long run need thicker wire?
Because thin wire loses voltage over distance, so a distant load may not get enough — long runs need thicker wire than the current alone implies.
Is a bigger gauge number thicker wire?
No — it is the opposite. Smaller gauge numbers mean thicker wire, which is a common source of confusion.
Is this a substitute for an electrician?
No — for mains or high-current wiring, follow the proper ratings and local electrical code, and use a qualified electrician where required.