What is AWG and what does the number mean?

AWG stands for American Wire Gauge, the standard sizing system for round electrical wire in North America. The number is an index into a geometric series, not a physical measurement. Each step changes the diameter by a fixed ratio, so AWG 14 is one notch thinner than AWG 13. Counter-intuitively the number runs backwards: a higher AWG is a thinner wire. AWG 24 telephone wire is far thinner than AWG 6 service cable.

How thick is AWG 12 wire?

AWG 12 has a bare copper diameter of about 2.05 mm (around 80.8 mils) and a cross-sectional area near 3.31 mm² (about 6530 kcmil expressed as circular mils, or 6.53 kcmil). It is a common choice for 20 amp household branch circuits in the United States. Type 12 into the By AWG number mode and the tool prints all of these figures at once so you can copy the exact value.

Why does a bigger AWG number mean a thinner wire?

The gauge originally counted how many times a wire was drawn through successively smaller dies, and more passes produced a thinner strand. The modern formula keeps that direction: diameter(mm) = 0.127 × 92^((36 − n) / 39). As n grows the exponent shrinks, so the diameter falls. That is why AWG 0 is fat at 8.25 mm while AWG 40 is hair-thin at 0.08 mm. For sizes thicker than 0 the notation flips to 1/0, 2/0, 3/0 and 4/0.

How do I work out the cross-sectional area from a gauge?

First get the diameter from the formula, then treat the conductor as a circle: area = π × (diameter / 2)². For AWG 10 that is π × (2.588 / 2)² ≈ 5.26 mm². The tool does both steps and also shows the area in kcmil (thousand circular mils), the unit cable spec sheets use. Remember this is the bare conductor area and ignores insulation thickness.

Can I trust the ampacity numbers for sizing a real circuit?

Treat them as a starting reference, not a final answer. The ampacity shown here is a commonly cited figure for copper, but real wire sizing depends on the insulation temperature rating, how many conductors are bundled together, the ambient temperature and the voltage drop over the run length. A short fan wire and a long buried feeder of the same gauge have very different safe currents. Always confirm against the applicable electrical code before you wire anything that matters.

How do I convert a measured diameter back to AWG?

Switch to the By diameter mode and type the millimetre reading from your calipers. The tool inverts the formula, n = 36 − 39 × log_92(diameter / 0.127), and snaps to the nearest standard gauge. A 2.05 mm strand comes back as AWG 12, an 8.2 mm one as 1/0. This is handy when you have a spool of unlabelled wire and need to match it to a connector or a circuit rating.

Pick a wire size for a DC project from current draw

You are wiring a 12 V LED strip pulling 6 amps over a short run and need to know the thinnest wire that is safe. Switch to By current, type 6, and the tool returns a reference gauge with its ampacity and area. You then check that figure against your run length and code rules before crimping connectors, instead of guessing from a spool you happen to have on the shelf.

Identify an unlabelled spool with calipers

A drawer full of mystery wire and no markings. Measure the bare conductor with calipers, switch to By diameter, and type the millimetre reading. A 2.05 mm strand snaps to AWG 12, an 8.2 mm one to 1/0. Now you can match it to a breaker rating or a connector spec sheet without trial and error on the bench.

Convert a US schematic to metric for an overseas build

A design calls for AWG 18 hookup wire but your local supplier sells by mm² cross-section. Type 18 in By AWG number, read the area in mm², and order the closest metric size. The tool shows diameter in both mm and mils so you can sanity-check against either spec sheet.

Estimate voltage drop and pick a heavier gauge

A long sensor run is reading low at the far end. The chart gives ohms per km for each gauge, so you can multiply by your run length to see the resistance, work out the drop at your current, and step up two gauges if it is too high. Copy the resistance figure straight into your voltage-drop math.

Teach or learn how AWG actually works

The reference chart from 4/0 to 40 sits right under the calculator, so a student can watch the diameter halve roughly every three gauges and see why the number runs backwards. Share the link with a study group and everyone lands on the same chart and example.

Wire Gauge Calculator (AWG): Diameter, Area, Ampacity

AWG to mm, area, ampacity and resistance, both ways, with a full 4/0 to 40 reference chart, browser-only

Runs locally
Category Calculator
Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.

Convert American Wire Gauge to diameter, area, ampacity and resistance — or work backwards from a measured diameter or a required current.

AWG gauge numberTry 12, 14, 0, or 4/0 (enter -3).

Result

Gauge

AWG 12

Diameter

2.0525 mm

80.8 mils

Area

3.3088 mm²

6.53 kcmil

Ampacity (ref)

~9.3 A

Resistance

5.211 Ω/km

Ampacity values are a rough reference only. Real wire sizing depends on insulation rating, bundling, ambient temperature and voltage drop — follow your local electrical code.

AWG reference chart

AWG	Diameter (mm)	Diameter (mils)	Area (mm²)	kcmil	Ampacity (A, ref)	Ω / km
4/0	11.684	460	107.219	211.6	302	0.161
3/0	10.405	409.6	85.029	167.81	239	0.203
2/0	9.266	364.8	67.431	133.08	190	0.256
1/0	8.252	324.9	53.475	105.53	150	0.322
1	7.348	289.3	42.408	83.69	119	0.407
2	6.544	257.6	33.631	66.37	94	0.513
3	5.827	229.4	26.671	52.63	75	0.647
4	5.189	204.3	21.151	41.74	60	0.815
5	4.621	181.9	16.773	33.1	47	1.028
6	4.115	162	13.302	26.25	37	1.296
7	3.665	144.3	10.549	20.82	30	1.634
8	3.264	128.5	8.366	16.51	24	2.061
9	2.906	114.4	6.634	13.09	19	2.599
10	2.588	101.9	5.261	10.38	15	3.277
11	2.305	90.7	4.172	8.23	12	4.132
12	2.053	80.8	3.309	6.53	9.3	5.211
13	1.828	72	2.624	5.18	7.4	6.571
14	1.628	64.1	2.081	4.11	5.9	8.286
15	1.45	57.1	1.65	3.26	4.7	10.45
16	1.291	50.8	1.309	2.58	3.7	13.17
17	1.15	45.3	1.038	2.05	2.9	16.61
18	1.024	40.3	0.823	1.62	2.3	20.95
19	0.912	35.9	0.653	1.29	1.8	26.42
20	0.812	32	0.518	1.02	1.5	33.31
21	0.723	28.5	0.411	0.81	1.2	42
22	0.644	25.3	0.326	0.64	0.92	52.96
23	0.573	22.6	0.258	0.51	0.73	66.79
24	0.511	20.1	0.205	0.4	0.58	84.22
25	0.455	17.9	0.162	0.32	0.46	106.2
26	0.405	15.9	0.129	0.25	0.36	133.9
27	0.361	14.2	0.102	0.2	0.29	168.9
28	0.321	12.6	0.081	0.16	0.23	212.9
29	0.286	11.3	0.064	0.13	0.18	268.5
30	0.255	10	0.051	0.1	0.14	338.6
31	0.227	8.9	0.04	0.08	0.11	426.9
32	0.202	8	0.032	0.06	0.091	538.3
33	0.18	7.1	0.025	0.05	0.072	678.8
34	0.16	6.3	0.02	0.04	0.057	856
35	0.143	5.6	0.016	0.03	0.045	1079
36	0.127	5	0.013	0.03	0.036	1361
37	0.113	4.5	0.01	0.02	0.028	1716
38	0.101	4	0.008	0.02	0.022	2164
39	0.09	3.5	0.006	0.01	0.018	2729
40	0.08	3.1	0.005	0.01	0.014	3441

What this tool does

Free AWG (American Wire Gauge) calculator that converts a gauge number into wire diameter, cross-sectional area, a reference ampacity and copper resistance, and runs the conversion in reverse from a measured diameter or a required current. The diameter formula is exact: diameter(mm) = 0.127 × 92^((36 − n) / 39), so a bigger AWG number always means a thinner wire, and the area follows from the circle. Three modes cover the questions you actually ask at the bench. By AWG number gives diameter in mm and mils, area in mm² and kcmil, plus ampacity and ohms per km. By diameter snaps a caliper reading to the nearest standard gauge. By current picks the thinnest reference gauge that carries the load. A built-in chart lists every size from 4/0 down to 40. Ampacity is a guidance figure, not a code table, and the tool says so. Everything runs in your browser with one click copy and a shareable link. 100% client-side, no upload.

Tool details

Input: Files + Numbers; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy + Preview; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 10 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Calculator · Developer; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How Wire Gauge Calculator (AWG) fits into your work

Use it for fast estimates, comparisons, and planning numbers before you make the final call.

Calculation jobs

Getting a realistic range before a purchase, plan, workout, or schedule decision.
Comparing scenarios by changing one input at a time.
Turning rough assumptions into a number you can discuss.

Calculation checks

Double-check units, dates, rates, and rounding assumptions.
Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
Save the inputs that produced an important result so you can reproduce it later.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Pick a wire size for a DC project from current draw
You are wiring a 12 V LED strip pulling 6 amps over a short run and need to know the thinnest wire that is safe. Switch to By current, type 6, and the tool returns a reference gauge with its ampacity and area. You then check that figure against your run length and code rules before crimping connectors, instead of guessing from a spool you happen to have on the shelf.
Identify an unlabelled spool with calipers
A drawer full of mystery wire and no markings. Measure the bare conductor with calipers, switch to By diameter, and type the millimetre reading. A 2.05 mm strand snaps to AWG 12, an 8.2 mm one to 1/0. Now you can match it to a breaker rating or a connector spec sheet without trial and error on the bench.
Convert a US schematic to metric for an overseas build
A design calls for AWG 18 hookup wire but your local supplier sells by mm² cross-section. Type 18 in By AWG number, read the area in mm², and order the closest metric size. The tool shows diameter in both mm and mils so you can sanity-check against either spec sheet.
Estimate voltage drop and pick a heavier gauge
A long sensor run is reading low at the far end. The chart gives ohms per km for each gauge, so you can multiply by your run length to see the resistance, work out the drop at your current, and step up two gauges if it is too high. Copy the resistance figure straight into your voltage-drop math.
Teach or learn how AWG actually works
The reference chart from 4/0 to 40 sits right under the calculator, so a student can watch the diameter halve roughly every three gauges and see why the number runs backwards. Share the link with a study group and everyone lands on the same chart and example.

Common pitfalls

Treating the ampacity column as a code-compliant rating. It is a reference figure only. Real sizing depends on insulation temperature rating, conductor bundling, ambient temperature and voltage drop over the run. A short jumper and a long buried feeder of the same gauge carry very different safe currents, so confirm against the applicable electrical code before you wire anything.
Reading the gauge number the wrong way round. A higher AWG is a thinner wire, not a thicker one. People grabbing AWG 18 expecting heavy cable and getting hookup-thin strand is a classic error. When in doubt, type the number into the calculator and look at the diameter in mm before you order.
Confusing diameter with cross-sectional area when converting to metric. Doubling the diameter quadruples the area, so a wire that is twice as wide is four times the mm², not twice. Use the area output, not the diameter, when matching to a mm² spec, and remember the figure is bare conductor and excludes insulation.

Privacy

Every calculation — the AWG diameter formula, the area, the reverse lookups and the chart — is plain JavaScript that runs in your browser tab. No gauge number, measurement or current value ever leaves the page, and nothing is logged. The one caveat: the shareable link encodes your mode and input in the query string, so a link pasted into chat records those values in the recipient server's access log. For anything you would rather keep private, use the copy button and paste the text instead of the URL.

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Wire Gauge Calculator (AWG): Diameter, Area, Ampacity

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Wire Gauge Calculator (AWG) fits into your work

Calculation jobs

Calculation checks

Good next steps

Real-world use cases

Pick a wire size for a DC project from current draw

Identify an unlabelled spool with calipers

Convert a US schematic to metric for an overseas build

Estimate voltage drop and pick a heavier gauge

Teach or learn how AWG actually works

Common pitfalls

Privacy

FAQ

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