Wire Gauge Converter
A larger AWG number means a thinner wire.
The scale runs backwards, for a reason
AWG numbers get larger as the wire gets thinner. AWG 10 is thick enough for a cooker circuit; AWG 30 is hair-fine.
The reason is manufacturing history. Wire is made by drawing a rod through a series of progressively smaller dies, and the gauge number counted how many times it had been drawn. More passes, thinner wire, higher number.
It is a geometric scale
AWG 36 is defined as 0.005 inches and AWG 0000 as 0.46 inches, with 39 steps between. Each step is therefore the 39th root of 92 — about 1.123 — so:
diameter (mm) = 0.127 × 92(36 − n) / 39
Two consequences worth memorising:
- Six gauges down doubles the diameter and quadruples the area.
- Three gauges down doubles the cross-sectional area, and therefore halves the resistance.
So AWG 10 has twice the copper of AWG 13 and four times that of AWG 16. That is a quicker way to reason about it than any table.
Area is what matters electrically
Resistance depends on cross-section, not diameter, and area goes with the square of the radius. Halving the diameter quarters the area and quadruples the resistance.
The resistance figure above is for copper at 20 °C. Aluminium is about 1.6 times more resistive, which is why aluminium wiring needs to be roughly two gauges thicker for the same job.
Metric wire is sized by area directly
European cable is specified in mm² of conductor — 1.0, 1.5, 2.5, 4.0 and so on. That is the honest way round, because mm² is the number that determines both resistance and current capacity.
Rough equivalents: 2.5 mm² is close to AWG 13, 1.5 mm² to AWG 15, and 1.0 mm² to AWG 17. None of them match exactly, which is a nuisance when working from a design in the other system.
Voltage drop over distance
The resistance-per-kilometre figure is the one that matters for long runs. A 30 m run of AWG 14 there and back is 60 m of copper at about 8.3 Ω/km, which is roughly half an ohm — enough to lose real voltage at high current. Long runs generally need a thicker cable than the current alone would suggest.
This converts between units. It does not tell you what cable a circuit needs: that depends on current, insulation, grouping, ambient temperature, installation method and local wiring regulations. For anything mains-connected, follow the applicable code or ask a qualified electrician.
Common uses
- Reading an American schematic with metric cable.
- Choosing hook-up wire for electronics.
- Estimating voltage drop on a long run.
- Matching a replacement to existing wiring.
Questions people ask
Why does a higher AWG number mean thinner wire?
Because the number counted how many times the wire was drawn through a die, and each pass made it thinner.
What is AWG 14 in mm²?
About 2.08 mm², with a diameter of 1.628 mm.
What is the rule of thumb for AWG steps?
Six gauges down doubles the diameter; three gauges down doubles the cross-sectional area and halves the resistance.
Does AWG map cleanly onto metric cable?
No. 2.5 mm² is close to AWG 13 and 1.5 mm² to AWG 15, but none match exactly.
Can I use this to choose cable for a circuit?
No. It converts units. Cable selection depends on current, insulation, grouping, temperature and local regulations — follow the applicable code.
Why does aluminium wiring need to be thicker?
Because it is about 1.6 times more resistive than copper, so it needs roughly two gauges more for the same job.
Worked out in the page
Nothing is sent anywhere. The tables are built into the page and the arithmetic runs in your browser, so it works with no connection.