Wire Gauge Calculator - AWG Size Reference & Specs

AWG ▲▼	Diameter (mm) ▲▼	Area (mm2) ▲▼	Ω/km ▲▼	Max A (chassis) ▲▼
4/0	11.684	107.2	0.1608	380
3/0	10.405	85.01	0.2028	328
2/0	9.266	67.43	0.2557	283
1/0	8.252	53.48	0.3224	245
1	7.348	42.41	0.4066	211
2	6.544	33.63	0.5127	181
3	5.827	26.67	0.6465	158
4	5.189	21.15	0.8152	135
6	4.115	13.3	1.296	101
8	3.264	8.367	2.061	73
10	2.588	5.261	3.277	55
12	2.053	3.309	5.211	41
14	1.628	2.081	8.286	32
16	1.291	1.309	13.17	22
18	1.024	0.8231	20.95	16
20	0.8128	0.5189	33.31	11
22	0.6438	0.3255	53.46	7
24	0.5106	0.2047	84.22	3.5
26	0.4049	0.1288	133.9	2.2
28	0.3211	0.081	212.9	0.83
30	0.2546	0.0509	338.6	0.52
32	0.2019	0.032	538.3	0.32
34	0.1601	0.0201	856	0.18
36	0.127	0.01267	1361	0.1
40	0.07987	0.00501	3441	0.036

How to use this tool

Select an AWG gauge from the dropdown or sortable reference table.
Review its wire specifications and enter run details to estimate copper voltage drop.

AWG wire gauge overview

The AWG (American Wire Gauge) system uses an inverse scale - lower numbers mean thicker wire. 4/0 (0000) is the largest common gauge; AWG 40 is fine enough for watch coils.

Choosing the right gauge

Match wire gauge to the maximum continuous current, not peak current.
Derate by 20–30% when bundling multiple conductors.
For long runs, consider voltage drop in addition to current capacity.

AWG to mm² conversion table

AWG	mm²	Typical use
18 AWG	0.82 mm²	Signal wiring, low-voltage lighting
14 AWG	2.08 mm²	General lighting circuits (15 A)
12 AWG	3.31 mm²	Standard outlets (20 A)
10 AWG	5.26 mm²	Dryers, EV charging (30 A)
6 AWG	13.3 mm²	Sub-panels, large appliances (55 A)

Voltage drop calculation

Excessive voltage drop can reduce equipment performance and cause lights to dim. NEC informational notes discuss 3% on branch circuits and 5% total (feeder + branch) as design guidance for efficiency; these are not mandatory universal limits and do not establish code compliance. This estimate uses the selected wire’s copper resistance at 20°C:

V_drop = I × R_per_km × length_km × factor
factor = 2 for DC or single-phase; √3 for balanced three-phase

For example, 20 A through a 50-foot one-way run of 12 AWG copper at 120 V in a single-phase circuit produces about 3.18 V of drop, or 2.65% of system voltage. That result is below the 3% reference for this run, but it does not evaluate a feeder plus branch or certify an installation.

Temperature rating and insulation types

NEC ampacity tables assume specific conductor temperature ratings. Common insulation types:

THHN: 90°C dry / 75°C wet; most common building wire in conduit.
THWN-2: 90°C wet; suitable for underground and outdoor conduit.
NM-B (Romex): 90°C conductors, but derated to 60°C in NM cable ampacity tables; used in residential walls.

When conduit is fully loaded (more than 3 current-carrying conductors), ampacity must be derated per NEC Table 310.15(B)(3)(a). High ambient temperatures (attics, boiler rooms) also require derating. The current values shown in the lookup table are simplified reference estimates, not NEC ampacity ratings; conductor material, insulation, installation method, ambient temperature, bundling, and local requirements all affect a safe design. Have a qualified electrician verify wiring for the actual installation.

Frequently asked questions

What is AWG?

AWG (American Wire Gauge) is a standardised wire gauge system used in North America. A lower AWG number means a thicker wire. 4/0 (0000) is the thickest standard gauge; 40 AWG is very fine.

What is the maximum current for a wire?

Maximum current depends on installation method. Chassis wiring (open air) allows higher current than wiring inside walls or conduit. Always derate for bundled cables or high ambient temperatures.

Diameter (mm / in)	2.053 / 0.0808
Cross-section area	3.309 mm²
Resistance (copper, 20°C)	5.211 Ω/km (0.005211 Ω/m)
Max current estimate - chassis / open air	41 A
Max current estimate - in-wall / conduit	20 A