Skip to main content

AWG to millimetres converter

When you need this

AWG is the American wire gauge scale. Conversion both ways: from the number and from the diameter.

d 1 mmAWGS
d — diameter over copper, S — cross-sectional area. The radius in the drawing is on a logarithmic scale
By AWG number
Gauge number: from −6 (0000000) to 50
Diameter over copper d
Cross-section S
Copper resistance per 100 m
By diameter in millimetres
Wire diameter over copper (mm)
Nearest AWG number
Exact value from the scale
Diameter of this gauge
Cross-section of the given wire

💡 Worth keeping in mind

Every three AWG numbers change the cross-section by about a factor of two, every six by four, every ten by ten. That is enough to work in your head: if AWG 20 is 0.5 mm², then AWG 14 is about 2 mm² and AWG 26 about 0.13 mm².

Enter the zero gauges either as a string of zeros or as a negative number: 00 = −1, 000 = −2, 0000 = −3. The resistance is for copper at DC: at radio frequencies the skin effect makes it much higher.

📐 Formulas​

The scale is geometric. Its anchors: #36 is 0.005″ in diameter and #0000 is 0.4600″, with exactly 39 steps of constant ratio between them. Hence:

d [mm] = 25.4 · 10^( −(n + 9.6954) / 19.8578 )
n = −19.8578 · log₁₀(d[mm] / 25.4) − 9.6954
S = π·d²/4
R = ρ·l / S,   ρ = 0.0175 Ω·mm²/m at +20 °C

The zero gauges. The thinner the wire, the larger the number; anything thicker than #0 is written with zeros:

Written asEnter
00
00−1
000−2
0000−3
00000−4
000000−5
0000000−6

The calculator takes either form — 0000 or -3.

Notation:​

  • n — the AWG gauge number
  • d — diameter over copper [mm]
  • S — cross-section [mm²]
  • R — resistance of copper per 100 m [Ω]
Limits of the calculator:
  • The resistance is for copper at DC: at radio frequencies the skin effect makes it much higher
  • The formula gives the nominal diameter over copper: real wire has a tolerance, and enamelled wire has insulation on top
  • The range of the calculator: from −6 (0000000) to 50

🎯 Where it is used​

  • Reading datasheets that give winding wire in AWG.
  • Finding a metric substitute for a wire quoted in AWG.
  • Estimating the resistance of a winding before you start winding it.
Practical notes:
  1. Every three AWG numbers change the cross-section by about a factor of two, every six by four, every ten by ten. That is enough to work in your head.
  2. Reference values: AWG 10 = 2.588 mm and 5.26 mm²; AWG 20 = 0.812 mm and 0.518 mm²; AWG 30 = 0.255 mm and 0.051 mm².
  3. For litz wire the AWG number refers to one strand, not the bundle: 105/48 AWG means 105 strands of gauge 48.

© 2026 UR3PKI · CyberDev.Space · Content licensed under CC BY-NC-SA 4.0.

How to cite this calculator
UR3PKI. «AWG to millimetres converter». CyberDev.Space. https://cyberdev.space/en/radio/calculators/coils/awg (licence CC BY-NC-SA 4.0).

The licence lets you use this material freely, including in teaching materials, but only with attribution to the author and a link to the source.

Last updated on