gauge to decimal Converter
A 14 gauge wire is 0.0641 inches as a decimal, and 1.628 mm in metric.
Quick answer: Multiply 0.005 by 92 raised to the power of (36 minus the gauge) over 39. For example, 14 AWG is 0.0641 in, 12 AWG is 0.0808 in and 18 AWG is 0.0403 in.
The gauge to decimal formula
Diameter in decimal inches equals 0.005 times 92 raised to the power of (36 minus the gauge) divided by 39.
Multiply the inches by 25.4 to get decimal millimetres.
Take 14 AWG. 0.005 × 92^((36 − 14) ÷ 39) gives 0.0641 in.
Take 12 AWG. 0.005 × 92^((36 − 12) ÷ 39) gives 0.0808 in.
Why a decimal is useful
A gauge number does not say how big a wire is until you turn it into a real size. The AWG rule gives 0.005 inches for 36 gauge and a fixed ratio for each step (Engineering ToolBox: AWG wire gauge vs circular mils).
A decimal is easy to compare with a caliper reading or a drawing.
How to convert gauge to decimal 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 0.005 for inches.
- Multiply by 25.4 for millimetres.
Example 1: 14 AWG
- Start with 14 AWG.
- 0.005 × 92^((36 − 14) ÷ 39) = 0.0641.
- The decimal size is 0.0641 in.
14 AWG = 0.0641 in
Example 2: 12 AWG
- Start with 12 AWG.
- 0.005 × 92^((36 − 12) ÷ 39) = 0.0808.
- The decimal size is 0.0808 in.
12 AWG = 0.0808 in
Example 3: 18 AWG
- Start with 18 AWG.
- 0.005 × 92^((36 − 18) ÷ 39) = 0.0403.
- The decimal size is 0.0403 in.
18 AWG = 0.0403 in
The three examples below use common sizes.
Each one shows the sum in full.
gauge to decimal conversion table
| Gauge | Decimal inches | Decimal millimetres |
|---|---|---|
| 4 AWG | 0.2043 in | 5.189 mm |
| 6 AWG | 0.162 in | 4.115 mm |
| 8 AWG | 0.1285 in | 3.264 mm |
| 10 AWG | 0.1019 in | 2.588 mm |
| 12 AWG | 0.0808 in | 2.053 mm |
| 14 AWG | 0.0641 in | 1.628 mm |
| 16 AWG | 0.0508 in | 1.291 mm |
| 18 AWG | 0.0403 in | 1.024 mm |
| 20 AWG | 0.032 in | 0.8118 mm |
| 22 AWG | 0.0253 in | 0.6438 mm |
| 24 AWG | 0.0201 in | 0.5106 mm |
| 26 AWG | 0.0159 in | 0.4049 mm |
| 28 AWG | 0.0126 in | 0.3211 mm |
The highlighted row is the default of the calculator. The last column gives mm.
A quick mental shortcut for gauge to decimal
Remember 12 AWG as about 0.081 inches and 18 AWG as about 0.040 inches.
Every 6 gauge steps halve or double the decimal.
How many decimals to keep
Four decimals of an inch is a good level for wire. So 14 AWG is 0.0641 inches.
If you need metric, two or three decimals of a millimetre are enough.
Worked values
A 10 AWG wire is about 0.1019 inches, and a 12 AWG wire is about 0.0808 inches.
A 20 AWG wire is about 0.0320 inches, and a 24 AWG wire is about 0.0201 inches.
Decimals and fractions
Decimals line up with a caliper. Fractions of an inch are better for a tape measure.
The fraction page shows the nearest sixty-fourth for each gauge.
Check with a caliper
Gauge is not a universal standard across metals, so measure when the fit matters (MachineMFG: Sheet metal gauge chart).
A reading on bare wire will confirm the decimal.
Quick conversion answers
| Conversion | Result |
|---|---|
| 14 AWG | 0.0641 in |
| 12 AWG | 0.0808 in |
| 18 AWG | 0.0403 in |
| 10 AWG | 0.1019 in |
Where this conversion is used
Machinists and makers compare gauge with a caliper reading.
Designers need a decimal size for a drawing.
Common mistakes to avoid
- Assuming a higher gauge is thicker. A higher gauge is thinner.
- Dropping a zero. 0.0641 is not 0.641.
- Using wire values for sheet metal. Sheet steel has its own table.
- Measuring over insulation. The gauge refers to the bare metal.
Related converters
Odd gauge sizes
3 AWG is 0.2294 in. 5 AWG is 0.1819 in. 7 AWG is 0.1443 in.
9 AWG is 0.1144 in. 11 AWG is 0.09074 in. 13 AWG is 0.07196 in.
15 AWG is 0.05707 in. 17 AWG is 0.04526 in. 19 AWG is 0.03589 in.
Thin wire sizes as decimals
24 AWG is 0.0201 in. 26 AWG is 0.01594 in. 28 AWG is 0.01264 in.
30 AWG is 0.01003 in. 32 AWG is 0.00795 in. 34 AWG is 0.006305 in.
A worked example in decimals
Take 12 AWG. Subtract 12 from 36 to get 24, and 24 divided by 39 is about 0.6154. Then 92 to that power is about 16.17, and times 0.005 gives about 0.0808 inches.
Multiply 0.0808 by 25.4 and you get about 2.05 mm. This matches the metric column.
Reading the decimals
A 20 AWG wire is about 0.0320 inches, which is about 0.812 mm. An 18 AWG wire is about 0.0403 inches, which is about 1.024 mm.
Compare the two. Going from 18 AWG to 20 AWG loses about 0.008 inches, so the steps get smaller as the wire gets thinner.
A decimal chart for thin wire
A 22 AWG wire is about 0.0253 inches and a 24 AWG wire is about 0.0201 inches. A 26 AWG wire is about 0.0159 inches.
A 28 AWG wire is about 0.0126 inches and a 30 AWG wire is about 0.0100 inches. A 32 AWG wire is about 0.0080 inches.
Using decimals in metric work
To turn a decimal in inches into millimetres, multiply by 25.4. So 0.0253 inches is about 0.644 mm and 0.0100 inches is about 0.255 mm.
To go the other way, divide millimetres by 25.4. So 2.053 mm is about 0.0808 inches.
Frequently asked questions
What is 14 gauge as a decimal?
About 0.0641 inches, or 1.628 mm.
What is 12 gauge as a decimal?
About 0.0808 inches, or 2.053 mm.
What is 18 gauge as a decimal?
About 0.0403 inches, or 1.024 mm.
How many decimals should I keep?
Four decimals of an inch is enough for wire.
Is a higher gauge a thinner wire?
Yes.
Is this the same for sheet metal?
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)
