gauge to diameter Converter
A 14 gauge wire is about 1.628 mm across, which gives a cross-section of about 2.08 mm2.
Quick answer: Raise 92 to the power of (36 minus the gauge) over 39, then multiply by 0.127. For example, 14 AWG is 1.628 mm, 12 AWG is 2.053 mm and 18 AWG is 1.024 mm.
The gauge to diameter formula
Diameter in millimetres equals 0.127 times 92 raised to the power of (36 minus the gauge) divided by 39.
This is the American Wire Gauge rule for solid round wire.
Take 14 AWG. 0.127 × 92^((36 − 14) ÷ 39) gives 1.628 mm.
Take 12 AWG. 0.127 × 92^((36 − 12) ÷ 39) gives 2.053 mm.
Gauge is a size code, not a length
Gauge is an old numbering scheme. Wire makers numbered sizes by the number of drawing passes, so a higher number means thinner wire (MachineMFG: Sheet metal gauge chart).
For AWG the diameter in millimetres is 0.127 times 92 to the power of (36 minus the gauge) over 39 (Engineering ToolBox: AWG wire gauge vs circular mils).
How to convert gauge to diameter step by step
- Confirm that the wire uses the American Wire Gauge.
- Subtract the gauge number from 36 and divide by 39.
- Raise 92 to that power and multiply by 0.127 for millimetres.
- Divide by 25.4 for inches.
Example 1: 14 AWG
- Start with 14 AWG.
- 0.127 × 92^((36 − 14) ÷ 39) = 1.628.
- The diameter is 1.628 mm.
14 AWG = 1.628 mm
Example 2: 12 AWG
- Start with 12 AWG.
- 0.127 × 92^((36 − 12) ÷ 39) = 2.053.
- The diameter is 2.053 mm.
12 AWG = 2.053 mm
Example 3: 18 AWG
- Start with 18 AWG.
- 0.127 × 92^((36 − 18) ÷ 39) = 1.024.
- The diameter is 1.024 mm.
18 AWG = 1.024 mm
The three examples below use common sizes.
Each one shows the sum in full.
gauge to diameter 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 | 0.8118 mm | 0.032 in |
| 22 AWG | 0.6438 mm | 0.0253 in |
| 24 AWG | 0.5106 mm | 0.0201 in |
| 26 AWG | 0.4049 mm | 0.0159 in |
| 28 AWG | 0.3211 mm | 0.0126 in |
The highlighted row is the default of the calculator. The last column gives in.
A quick mental shortcut for gauge to diameter
Remember that 12 AWG is about 2 mm across and 18 AWG is about 1 mm.
Every 6 gauge steps halve or double the diameter, so 24 AWG is about 0.5 mm.
Diameter and area
The cross-section of a round wire is pi divided by 4 times the diameter squared. For 14 AWG that is about 2.081 mm2, and for 10 AWG it is about 5.261 mm2 (Engineering ToolBox: AWG wire gauge vs circular mils).
Three gauge steps roughly halve the area, which is why a small step in gauge matters so much.
Very large wire
The same formula works for gauge 0, which is 1/0 and measures about 8.251 mm. Gauge -3 stands for 4/0 and measures about 11.684 mm, which is 0.46 inches.
The calculator accepts 0, -1, -2 and -3 for these sizes.
Solid and stranded wire
The formula describes a single solid round wire. Stranded cable is made of many thin strands, so its overall size can differ.
Check the maker data sheet when the fit matters.
Check with a tool
Gauge is not a universal standard across metals, so measure when the size matters (MachineMFG: Sheet metal gauge chart).
A caliper on bare wire will confirm the diameter.
Quick conversion answers
| Conversion | Result |
|---|---|
| 14 AWG | 1.628 mm |
| 12 AWG | 2.053 mm |
| 18 AWG | 1.024 mm |
| 10 AWG | 2.588 mm |
Where this conversion is used
Electricians check that a wire fits a terminal or a conduit.
Makers match wire to jewellery or craft parts.
Common mistakes to avoid
- Assuming a higher gauge is thicker. A higher gauge is thinner.
- Mixing gauge systems. Sheet steel and wire use different scales.
- Measuring over the insulation. The gauge refers to the bare metal.
- Applying the formula to stranded cable. It is for solid round wire.
Related converters
Odd gauge sizes
3 AWG is 5.827 mm. 5 AWG is 4.621 mm. 7 AWG is 3.665 mm.
9 AWG is 2.906 mm. 11 AWG is 2.305 mm. 13 AWG is 1.828 mm.
15 AWG is 1.45 mm. 17 AWG is 1.15 mm. 19 AWG is 0.9116 mm.
Cross-section area for common gauges
4 AWG is 21.15 mm2. 6 AWG is 13.3 mm2. 8 AWG is 8.366 mm2.
10 AWG is 5.261 mm2. 12 AWG is 3.309 mm2. 14 AWG is 2.081 mm2.
16 AWG is 1.309 mm2. 18 AWG is 0.823 mm2.
Two more worked examples
Take 16 AWG. Subtract 16 from 36 to get 20, and 20 divided by 39 is about 0.5128. Then 92 to that power is about 10.16, and times 0.127 gives about 1.291 mm.
Take 22 AWG. Subtract 22 from 36 to get 14, and 14 divided by 39 is about 0.3590. Then 92 to that power is about 5.07, and times 0.127 gives about 0.644 mm.
Check the pair. Going from 10 AWG at 2.588 mm to 16 AWG at 1.291 mm halves the diameter, which matches the six step rule.
Reading the size change
Each gauge step changes the diameter by a ratio of about 1.1229. Two steps give about 1.261, so 12 AWG at 2.053 mm is about 1.261 times 14 AWG at 1.628 mm.
Use this to sense check a result. A thicker wire always has a lower gauge number.
Frequently asked questions
How do I convert gauge to diameter?
Use d = 0.127 x 92^((36 – n) / 39) for diameter in mm.
What is the diameter of 14 gauge wire?
About 1.628 mm, or 0.0641 inches.
What is the diameter of 12 gauge wire?
About 2.053 mm, or 0.0808 inches.
Does a higher gauge mean thicker wire?
No. A higher gauge number is a thinner wire.
How much does the diameter change per gauge step?
By a ratio of about 1.1229 for each step.
Is this the same as sheet metal gauge?
No. Sheet steel has its own table.
Sources
- Engineering ToolBox: AWG wire gauge vs circular mils (engineeringtoolbox.com)
- MachineMFG: Sheet metal gauge chart (machinemfg.com)
