Reference chart

AWG wire gauge chart

AWG numbers run backwards: the bigger the gauge, the thinner the wire. This chart gives each copper gauge's diameter, cross-section and resistance per metre, the metric sizes beside them, and a rough guide to the current each one can carry.

AWG 10 to 30

Resistance is for one metre of solid copper at 20 °C. Count the wire out and back: a load 5 m away has 10 m of wire in its loop.

AWG	Diameter	Area	Resistance per metre
10	2.59 mm	5.26 mm²	3.19 mΩ
11	2.30 mm	4.17 mm²	4.03 mΩ
12	2.05 mm	3.31 mm²	5.08 mΩ
13	1.83 mm	2.62 mm²	6.40 mΩ
14	1.63 mm	2.08 mm²	8.07 mΩ
15	1.45 mm	1.65 mm²	10.2 mΩ
16	1.29 mm	1.31 mm²	12.8 mΩ
17	1.15 mm	1.04 mm²	16.2 mΩ
18	1.02 mm	0.823 mm²	20.4 mΩ
19	0.91 mm	0.653 mm²	25.7 mΩ
20	0.81 mm	0.518 mm²	32.5 mΩ
21	0.72 mm	0.410 mm²	40.9 mΩ
22	0.64 mm	0.326 mm²	51.6 mΩ
23	0.57 mm	0.258 mm²	65.1 mΩ
24	0.51 mm	0.205 mm²	82.1 mΩ
25	0.45 mm	0.162 mm²	103 mΩ
26	0.40 mm	0.129 mm²	130 mΩ
27	0.36 mm	0.102 mm²	165 mΩ
28	0.32 mm	0.081 mm²	207 mΩ
29	0.29 mm	0.064 mm²	262 mΩ
30	0.25 mm	0.051 mm²	330 mΩ

Two handy patterns: every three gauges halves the area and doubles the resistance, and every ten gauges is ten times the area.

Metric cable sizes

Outside North America, cable is sold by its cross-section in mm². The diameter here is for a single solid core; stranded cable of the same size is a little fatter.

Size	Diameter	Resistance per metre	Nearest AWG
0.5 mm²	0.80 mm	33.6 mΩ	20
0.75 mm²	0.98 mm	22.4 mΩ	18
1 mm²	1.13 mm	16.8 mΩ	17
1.5 mm²	1.38 mm	11.2 mΩ	15
2.5 mm²	1.78 mm	6.72 mΩ	13
4 mm²	2.26 mm	4.20 mΩ	11
6 mm²	2.76 mm	2.80 mΩ	9

The resistances use copper's resistivity of 0.0168 Ω for a metre of 1 mm² wire, the same figure as the lessons and the calculator. Some published tables use 0.0172, a few percent higher, and copper's resistance rises about 0.4% for every degree it warms up.

How much current?

The current a wire can carry safely depends on its insulation, how hot the room is, whether it's bundled with other wires, and how long it is. Treat these as a cautious starting point for short runs, not a rating:

AWG	Typical use	A cautious current
28–30	Ribbon cable, wire-wrap, signals	Up to about 0.5 A
22–24	Breadboard hook-up wire, sensors	Up to about 1 A
18–20	LED strips, small motors	Up to about 5 A
16	12 V accessories, speaker cable	Up to about 10 A
14	Mains lighting circuits (USA)	15 A
12	Mains socket circuits (USA)	20 A
10	Heavy 12 V runs, battery leads	30 A

Flexible mains cords in metric sizes are commonly rated 3 A for 0.5 mm², 6 A for 0.75 mm², 10 A for 1 mm², 16 A for 1.5 mm², 25 A for 2.5 mm² and 32 A for 4 mm².

Picking a wire

Find the current the load draws.
Pick a size from the current table that carries it with room to spare.
Check the voltage drop: resistance per metre × the length out and back × the current.

A 12 V LED strip draws 2 A, 5 m from its supply. In 22 AWG the loop is 10 × 0.0516 = 0.52 Ω, which drops about 1 V: 9% of 12 V, and the far end looks dim. In 16 AWG it's 0.13 Ω and about 0.26 V, 2%. On low voltages the drop, not the heat, usually sets the size.

Free lesson

Now build it yourself

Each lesson comes in three short parts: see the idea, try it on a live board, then build it yourself, with quick checks as you go.

Try it yourself: free lesson

“Lost in the wire” is lesson 4 of 6 in Watt Harbour, Power & Energy World 1. Free with an account. Lessons unlock in order, so you’ll do the 3 before it first.

Or start from the very first lesson, no account needed

Work it out

Wire voltage drop calculatorVolts and watts lost in a cable, out and back, and the size that keeps it under 3%.

The ideas behind it

How to calculate voltage drop in a wireA wire is a resistor: how many volts a cable steals, the heat it makes, and why the grid runs at high voltage.

Questions people ask

Why does a bigger AWG number mean a thinner wire?

The numbers began as a count of drawing steps: each pass through a smaller hole made the wire thinner and added one to the gauge. Every three gauges halves the copper: 22 AWG has about half the cross-section of 19 AWG, and twice the resistance.

What is 22 AWG in mm²?

About 0.33 mm², 0.64 mm across. It's the usual solid hook-up wire for breadboards. It has about 52 mΩ per metre, so a metre of it drops about 0.05 V at 1 A.

What size wire do I need for 10 A at 12 V?

For a short run, 16 AWG or 1.5 mm² is a common choice. Over a longer run, check the voltage drop too: a lamp 5 m away has 10 m of wire in its loop, and 10 m of 1.5 mm² drops about 1.1 V at 10 A, 9% of 12 V. Go up to 2.5 or 4 mm².

Is stranded wire the same as solid wire of the same gauge?

It has about the same copper, so about the same resistance, but it's a little fatter and far more flexible. Use solid wire for breadboards and stranded wire for anything that moves or bends.