AWG to mm²
Convert American Wire Gauge to conductor cross section in mm² using ASTM B258. Gauge 4/0 is n = -3. This is diameter geometry, not a code ampacity table.
Rated 4.7 out of 5 based on 328 reviews
How to convert AWG to mm²
- Enter the AWG number. The default is 12. Use -3 for 4/0, -2 for 3/0, -1 for 2/0, and 0 for 1/0.
- Keep From as AWG and To as mm², or pick kcmil for thousand circular mils.
- Read mm² and the diameter row. The formula is ASTM B258: d(in) = 0.005 × 92^((36-n)/39).
- Swap units to estimate AWG from a mm² figure. Check voltage drop on the voltage drop calculator, not here.
American Wire Gauge
Solid conductor diameter (ASTM B258)
| AWG number n | Integer from 4/0 (n = -3) to 40 |
|---|---|
| Diameter | d(in) = 0.005 × 92^((36-n)/39) |
| mm² | Area of a circle with that diameter, π(d/2)² |
| Circular mil | Area in mils squared. 1 kcmil = 1000 circular mils |
| 4/0 | Also written 0000, n = -3 on this page |
| Ampacity | Not computed. Codes and temperature change current rating |
What AWG to mm² does
American Wire Gauge (AWG) numbers a solid round conductor by a geometric diameter rule in ASTM B258: d(in) = 0.005 × 92 raised to (36-n)/39. Gauge 36 is 0.005 in. Gauge 4/0 (0000) is n = -3. This page turns that diameter into square millimeters (the circle area) and into kcmil (thousand circular mils). The default input is 12 AWG, a common building-wire size in conversation, still not a permission to load a circuit.
Length units that are not wire sit on length. Circuit voltage drop is voltage drop. This page is not that calculator and not an ampacity table from NEC or IEC.
ASTM B258 and area
d(in) = 0.005 × 92^((36-n)/39). d(mm) = d(in) × 25.4. mm² = π × (d(mm)/2)². Circular mils = (d in mils)². kcmil = circular mils / 1000. From mm² back to AWG the engine inverts the diameter rule and may return a non-integer n. Solid copper is the model. Stranded constructions use a different effective diameter.
AWG, circular mil, and mm²
North American sheets quote AWG or kcmil. Metric sheets quote mm². They describe the same kind of quantity (cross section) only after you assume a round solid. A 10 mm² IEC cable is not a named AWG size. The nearest AWG is an estimate. Ampacity depends on insulation, bundling, ambient temperature, and the code you follow. None of those inputs are here.
When to convert AWG to mm² here
Read 12 AWG as mm², check 4/0 as kcmil, or estimate AWG from a metric area. Run voltage drop with length, current, and gauge on the voltage drop calculator. Leave length in inches on inches to cm.
What this page does not do
It is not a code ampacity table. It does not compute voltage drop. It does not model stranded or compact conductors. It is not wiring advice. Input stays in this tab.