Fundamentals calculator
AWG ⇄ mm² ⇄ kcmil Wire Size Converter
Convert between AWG, kcmil and mm², with diameter and the nearest standard size in each system.
BasicsBasis: ASTM B258 (AWG) · IEC 60228 (metric sizes)
Results
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Formula
d (mm) = 0.127 × 92(36 − n)/39, where n is the gauge (1/0 = 0, 2/0 = −1, 3/0 = −2, 4/0 = −3).
A (mm²) = π d² / 4 1 kcmil = 0.5067 mm² kcmil = d(mils)² / 1000
Worked example
10 AWG: d = 0.127 × 9226/39 = 2.588 mm, A = 5.26 mm², which is 10.38 kcmil. The nearest larger IEC size is 6 mm².
Assumptions and standards
- AWG figures are for solid round conductors; stranded conductors of the same gauge have a slightly larger overall diameter.
- AWG and metric sizes are not exact equivalents. When substituting, choose the next larger size and recheck ampacity and voltage drop.
Formula and data last verified: October 2026.
Frequently asked questions
Is 2.5 mm² the same as 14 AWG?
Not exactly. 14 AWG is 2.08 mm² and 12 AWG is 3.31 mm², so 2.5 mm² sits between them. Always round up to the larger conductor when substituting.
What is kcmil?
Thousands of circular mils. One circular mil is the area of a circle 1 mil (0.001 in) in diameter. North American conductors larger than 4/0 AWG are sized in kcmil.
Can I use these results for final design?
Use them for preliminary design and checking. Final designs must be verified by a qualified engineer against the code edition and standards adopted where the work is installed.
Is my data sent anywhere?
No. Every calculation runs in your browser. Nothing you type is uploaded or stored on our servers.