Gauge To mm Converter
A 12 gauge wire is thicker than a 20 gauge wire, which seems backwards until you learn that the scale counts how many times the wire was drawn through a die.
Quick answer: for American Wire Gauge, the diameter in millimetres is 0.127 × 92^((36 − gauge) ÷ 39). So 12 AWG is 2.053 mm, 14 AWG is 1.628 mm and 18 AWG is 1.024 mm.
The gauge to millimetres formula
For American Wire Gauge, the diameter in millimetres is 0.127 times 92 raised to the power of (36 minus the gauge) divided by 39 (Wikipedia: American wire gauge).
A larger gauge number means a thinner wire, and the scale is not linear, so a table or the formula is needed.
For 12 AWG, 36 − 12 is 24, 24 ÷ 39 is 0.6154, 92 to that power is about 16.17, and 16.17 × 0.127 is 2.053 mm.
For 18 AWG, the same steps give 1.024 mm.
What gauge means
Gauge is an old numbering scheme for the thickness of wire, sheet and tubing. In American Wire Gauge, 36 AWG is 0.005 in thick and 0000 AWG is 0.46 in, a ratio of about 92 (Wikipedia: American wire gauge).
Each step in gauge changes the diameter by the same ratio, about 1.1229, so six gauge steps roughly halve or double the diameter.
Different industries use different gauge systems, so a 14 gauge sheet is not the same thickness as 14 gauge wire.
How to convert gauge to mm step by step
- Confirm which gauge system applies, such as AWG for wire.
- Subtract the gauge number from 36.
- Divide by 39 and raise 92 to that power.
- Multiply by 0.127 to get millimetres.
Example 1: 12 AWG wire
- Start with n = 12.
- 92^(24 ÷ 39) = about 16.17.
- 16.17 × 0.127 = 2.053 mm.
12 AWG = 2.053 mm
Example 2: 18 AWG wire
- Start with n = 18.
- 92^(18 ÷ 39) = about 8.06.
- 8.06 × 0.127 = 1.024 mm.
18 AWG = 1.024 mm
Example 3: 10 AWG wire
- Start with n = 10.
- 92^(26 ÷ 39) = about 20.38.
- 20.38 × 0.127 = 2.588 mm.
10 AWG = 2.588 mm
These values describe solid round copper wire, and stranded cable measures slightly larger.
gauge to mm conversion table
| Gauge | Diameter (mm) | Diameter (in) |
|---|---|---|
| 4 AWG | 5.189 mm | 0.2043 in |
| 6 AWG | 4.115 mm | 0.162 in |
| 8 AWG | 3.264 mm | 0.1285 in |
| 10 AWG | 2.588 mm | 0.1019 in |
| 12 AWG | 2.053 mm | 0.0808 in |
| 14 AWG | 1.628 mm | 0.0641 in |
| 16 AWG | 1.291 mm | 0.0508 in |
| 18 AWG | 1.024 mm | 0.0403 in |
| 20 AWG | 0.812 mm | 0.032 in |
| 22 AWG | 0.644 mm | 0.0253 in |
| 24 AWG | 0.511 mm | 0.0201 in |
| 26 AWG | 0.405 mm | 0.0159 in |
| 28 AWG | 0.321 mm | 0.0126 in |
| 30 AWG | 0.255 mm | 0.01 in |
| 32 AWG | 0.202 mm | 0.008 in |
The highlighted row is 12 AWG, a common household wire. Notice how every six gauge steps roughly halve the diameter.
A quick mental shortcut for gauge to mm
Every 6 gauge steps halve or double the diameter, and every 3 steps halve or double the cross-sectional area. So 18 AWG is about half the diameter of 12 AWG.
Remember 12 AWG as 2 mm and 18 AWG as 1 mm for a quick check.
Which gauge system are you using
Wire, sheet metal, needles, shotguns and body jewellery all use gauge, and the scales differ. A single chart cannot serve them all, which is the most common cause of wrong sizes (BrightChamps: Gauge to mm conversion).
American Wire Gauge is also close to the older Brown and Sharpe scale, while Standard Wire Gauge uses different numbers.
Gauge, diameter and area
Because thickness drops by a fixed ratio, area drops faster. Three gauge steps halve the area, which is why 10 AWG carries far more current than 16 AWG.
Always check the wire rating for load rather than guessing from diameter alone.
Gauge to mm for jewellery and crafts
Body jewellery uses the same AWG sizes, so 14 gauge is about 1.6 mm and 2 gauge is about 6.5 mm. Crafters use gauge for beading wire and jewellery wire in the same way.
Always confirm with a caliper if a close fit matters.
Checking your answer
Divide the millimetres by 25.4 to see inches, and compare with a trusted chart. The values should fall as the gauge number rises.
If your result grows with the gauge number, the exponent was applied the wrong way.
Worked AWG values
A 12 gauge wire is about 2.053 mm across, and a 20 gauge wire is about 0.812 mm.
Always check which gauge system the product uses before you convert.
Quick conversion answers
| Conversion | Result |
|---|---|
| 10 gauge to mm | 2.588 mm |
| 12 gauge to mm | 2.053 mm |
| 14 gauge to mm | 1.628 mm |
| 16 gauge to mm | 1.291 mm |
| 18 gauge to mm | 1.024 mm |
| 20 gauge to mm | 0.812 mm |
Where this conversion is used
Electricians and DIYers choose wire for circuits and extension leads.
Makers and jewellers pick wire and jewellery sizes.
Students convert gauge numbers to real diameters.
Common mistakes to avoid
- Assuming bigger gauge means thicker. A higher gauge is thinner.
- Mixing gauge systems. Wire, sheet and needle gauges differ.
- Ignoring insulation. Measure bare conductor for diameter.
- Rounding too early. Keep three decimals.
Related converters
Frequently asked questions
How many mm is 10 gauge wire?
About 2.588 mm for 10 AWG.
How many mm is 12 gauge?
About 2.053 mm for 12 AWG.
Is 18 gauge wire thick?
No. 18 AWG is about 1.024 mm, which is thin.
What is the rule of thumb for wire gauge?
Every 6 steps halve the diameter and every 3 steps halve the area.
How is SWG different from AWG?
SWG is a separate scale with different sizes, so the numbers are not interchangeable.
Is the same gauge the same thickness for sheet metal?
No. Sheet metal uses different gauge tables.
Sources
- Wikipedia: American wire gauge (en.wikipedia.org)
- BrightChamps: Gauge to mm conversion (brightchamps.com)
