Why AWG isn't a straight-line scale
AWG numbers don't step in equal amounts of size — each gauge is a fixed ratio smaller than the one before it, so the numbers form a geometric (not linear) sequence. Going up 3 AWG numbers roughly halves the cross-sectional area, which is why wire tables jump unevenly between adjacent gauges.
- n — AWG number (lower = thicker; 36 is the reference gauge)
- d — diameter (mm)
- A — cross-sectional area (mm²)
Common values
| AWG number | Diameter |
|---|---|
| 2 | 6.544 mm |
| 5 | 4.621 mm |
| 10 | 2.588 mm |
| 20 | 0.812 mm |
| 30 | 0.255 mm |
More detail
Why every 3 gauges roughly halves the area
The AWG scale is built so 92 is the ratio between the two gauges the scale is anchored to — 0000 (0.46 in) and 36 (0.005 in) — across 39 steps — a ratio of 92^(1/39) ≈ 1.123 in diameter per step. Because area scales with diameter squared, three steps multiply the area by roughly 1 / (92^(3/39))² ≈ 0.5, which is the rule of thumb electricians use: +3 AWG ≈ half the copper, −3 AWG ≈ double the copper.
Reading a spec sheet. If a datasheet gives you a bare diameter or cross-section instead of an AWG number, switch to "Diameter (mm) → AWG" above — the result won't always land on a whole number, since real wire is drawn to a nominal size that can sit slightly off the ideal AWG curve.
Frequently asked questions
What is AWG 20 wire in mm?
AWG 20 has a diameter of 0.127 × 92^((36−20)/39) ≈ 0.812 mm and a cross-sectional area of (π/4) × 0.812² ≈ 0.518 mm² — a size commonly used for signal wiring and low-current hookup wire.
A wire measures 1 mm across — what AWG is that closest to?
Switch to "Diameter (mm) → AWG", enter 1: n = 36 − 39·log₉₂(1 / 0.127) ≈ 18.2, so it sits closest to AWG 18 (18 has a slightly larger diameter, 1.024 mm).
Why does AWG 0000 ("4/0") have a negative number in this calculator?
AWG continues below 0 for the thickest standard gauges, traditionally written 0, 00, 000, 0000. This calculator represents them as 0, −1, −2, −3 so the same formula covers the whole range; 0000 (n = −3) works out to exactly 0.127 × 92 = 11.684 mm.
Does a thicker AWG number mean a thicker wire?
No — it's reversed. Lower AWG numbers are thicker wire; AWG 10 carries far more current than AWG 24. Going from AWG 24 to AWG 21 (a smaller number) roughly doubles the cross-sectional area for the same reason three gauges ≈ a 2× area change.