Comprehensive AWG Wire Size & Ampacity Guide – Standard Chart for Accurate Electrical Sizing

AWG – American Wire Gauge Chart – Wire Size & Amps Rating Table

American Wire Gauge “AWG” is one of the important and standard tools in the US NEC (National Electrical Codes) used to sizing different cables and wires for multiple applications. Similarly to the SWG (Standard Wire Gauge) used in the UK, AWG is used to determine the ampacity of copper and aluminum wires for electrical wiring installations etc.

The AWG tables and charts are handy methods to specify the current carrying capacity of a conductor, its diameter, resistance, max current in amperes and other important parameters and characteristics.

AWG – American Wire Gauge

It is impossible to measure the exact amount of resistance in ohms of a wire having specific length for precise wire diameter. That’s where the AWG (American Wire Gauge) has played an important role since 1857.

The AWG is used to exactly measure the diameter of a particular conductor (such as solid, stranded, round and non-ferrous (alloys or metals that do not contain any appreciable amounts of iron) materials e.g. Aluminum, Copper etc). One of the most important roles of American Wire Gauge is to measure the current carrying capacity in Amps of wire (aka Wire Ampacity = The amount of maximum current that a conductor can carry continuously without exceeding its temperature rating.

One thing should be noted about the AWG that the larger the integer, the smaller the thickness and diameter of wire. For example, the 14AWG size is a suitable wire for a 15Amp circuit breaker, whereas the 8AWG size is most appropriate for 40Amps of circuit breakers and load points. In short, the ampacity is inversely proportional to the size of AWG integers (from 0000AWG to 40AWG) e.g. the higher the AWG size, the lower the ampacity and vise versa.

Good to know: The American Wire Gauge (AWG) is also known as B and S Gauge (Brown & Sharpe Gauge).

The Wire Gauge (Measuring Tool)

If you are on the job site and need to know the wire size gauge for the particular load, one of the quick solutions is to use the handy device known as wire gauge tool. It is a small circular shaped disc where different but common numbers are printed on it in accordance with the specific slots and holes.

To use the wire gauge tool to find the suitable gauge size for a particular wire, simply remove the outer insulation and insert the wire conductor in the wire gauge slot one by one. If it is fixed properly in the slot (not hole), this is the exact gauge size (printed on that specific slot) of the wire.

 

Why are Wire Gauge Charts & Tables Important?

In any electrical installation system whether domestic or industrial, the selection of proper wire size and appropriate size of circuit breaker is very important. For example, if you need to install a water heater, what size of wire will you select? As you can’t use the same size of wire for all the electrical load points and higher wattage appliances. If so, the small wire for higher load may get hotter which leads to burn the wire as well as damage the circuit breaker and connected appliance to it. That’s where we need an AWG tool and related charts and tables to it.

Based on the wire size chart, you may select an “8 AWG” wire size and 50A of circuit breaker for 240V, 9000W, 240V water heater element wattage. We will show a solved example as well as the related AWG Wire size table for this in the following sections.

Related Calculators: 

• Wire & Cable Size Calculator in AWG
• Electrical Wire & Cable Size Calculator (Copper & Aluminum)

Wire Gauge Chart & Table – AWG Gauge

The integers (as numbers) printed on the American Wire Gauge shows the gauge size. In AWG, there are a total of 44 gauges assigned to different numbers. In the list of standard sizes as integers, 4/0 (0000) is the largest diameter and 40AWG is the smallest diameter printed on AWG.

In addition, there are some special gauges such as 0000 (4/0), 000 (3/0), 00 (2/0) used for wire diameter and thickness larger than 0AWG. Instead of these complex stuff, wire gauge tables and charts are the alternative helpful resources based on the AWG. In these AWG gauge charts, most common gauge values show the different characteristics of wire such as its diameter, area, ampacity, resistance, current density, fusing current and temperature ratings etc.

The following AWG “American Wire Gauge” table shows the AWG Size and diameter in millimeter “mm” and inches in “in”, its cross sectional area in mm², Inche² and kcmil or MCM and resistance in ohms per 1000 feet and 1000 meter. The AWG size chart also shows the current in amperes for chassis wiring and power transfer application.

AWG #	Diameter		Cross Section Area			Resistance in Ω		Current in Amps
	mm	inch	mm2	Inch2	kcmil	Ω / kft	Ω / km	Chassis Wiring	Power Transfer
0000 (4/0)	11.6840	0.4600	107.2193	0.1662	211.6000	0.049	0.1608	380	302
000 (3/0)	10.4049	0.4096	85.0288	0.1318	167.8064	0.0618	0.2028	328	239
00 (2/0)	9.2658	0.3648	67.4309	0.1045	133.0765	0.0779	0.2557	283	190
0 (1/0)	8.2515	0.3249	53.4751	0.0829	105.5345	0.0983	0.3224	245	150
1	7.3481	0.2893	42.4077	0.0657	83.6927	0.1239	0.4066	211	119
2	6.5437	0.2576	33.6308	0.0521	66.3713	0.1563	0.5127	181	94
3	5.8273	0.2294	26.6705	0.0413	52.6348	0.197	0.6464	158	75
4	5.1894	0.2043	21.1506	0.0328	41.7413	0.2485	0.8152	135	60
5	4.6213	0.1819	16.7732	0.0260	33.1024	0.3133	1.028	118	47
6	4.1154	0.1620	13.3018	0.0206	26.2514	0.3951	1.296	101	37
7	3.6649	0.1443	10.5488	0.0164	20.8183	0.4982	1.634	89	30
8	3.2636	0.1285	8.3656	0.0130	16.5097	0.6282	2.061	73	24
9	2.9064	0.1144	6.6342	0.0103	13.0927	0.7921	2.599	64	19
10	2.5882	0.1019	5.2612	0.0082	10.3830	0.9988	3.277	55	15
11	2.3048	0.0907	4.1723	0.0065	8.2341	1.26	4.132	47	12
12	2.0525	0.0808	3.3088	0.0051	6.5299	1.588	5.211	41	9.3
13	1.8278	0.0720	2.6240	0.0041	5.1785	2.003	6.571	35	7.4
14	1.6277	0.0641	2.0809	0.0032	4.1067	2.525	8.285	32	5.9
15	1.4495	0.0571	1.6502	0.0026	3.2568	3.184	10.448	28	4.7
16	1.2908	0.0508	1.3087	0.0020	2.5827	4.015	13.174	22	3.7
17	1.1495	0.0453	1.0378	0.0016	2.0482	5.063	16.612	19	2.9
18	1.0237	0.0403	0.8230	0.0013	1.6243	6.385	20.948	16	2.3
19	0.9116	0.0359	0.6527	0.0010	1.2881	8.051	26.415	14	1.8
20	0.8118	0.0320	0.5176	0.0008	1.0215	10.152	33.308	11	1.5
21	0.7229	0.0285	0.4105	0.0006	0.8101	12.802	42.001	9	1.2
22	0.6438	0.0253	0.3255	0.0005	0.6424	16.143	52.962	7	0.92
23	0.5733	0.0226	0.2582	0.0004	0.5095	20.356	66.784	4.7	0.729
24	0.5106	0.0201	0.2047	0.0003	0.4040	25.668	84.213	3.5	0.577
25	0.4547	0.0179	0.1624	0.0003	0.3204	32.367	106.19	2.7	0.457
26	0.4049	0.0159	0.1288	0.00025	0.2541	40.814	133.9	2.2	0.361
27	0.3606	0.0142	0.1021	0.00020	0.2015	51.466	168.85	1.7	0.288
28	0.3211	0.0126	0.0810	0.00013	0.1598	64.897	212.92	1.4	0.226
29	0.2859	0.0113	0.0642	0.00010	0.1267	81.833	268.48	1.2	0.182
30	0.2546	0.0100	0.0509	0.00008	0.1005	103.19	338.55	0.86	0.142
31	0.2268	0.0089	0.0404	0.00006	0.0797	130.12	426.9	0.7	0.113
32	0.2019	0.0080	0.0320	0.00005	0.0632	164.08	538.32	0.53	0.091
33	0.1798	0.0071	0.0254	0.00004	0.0501	206.9	678.8	0.51	0.088
34	0.1601	0.0063	0.0201	0.000031	0.0398	260.9	855.96	0.43	0.072
35	0.1426	0.0056	0.0160	0.000025	0.0315	328.98	1,079.3	0.43	0.072
36	0.1270	0.0050	0.0127	0.000020	0.0250	414.84	1,361	0.33	0.056
37	0.1131	0.0045	0.0100	0.000016	0.0198	523.1	1,716.2	0.33	0.056
38	0.1007	0.0040	0.0080	0.000012	0.0157	659.62	2,164.1	0.27	0.044
39	0.0897	0.0035	0.0063	0.000010	0.0125	831.77	2,728.9	0.26	0.043
40	0.0799	0.0031	0.0050	0.000008	0.0099	1,048.8	3,441.1	0.21	0.035

Note: Resistance of wires in Ω/km and Ω/kft are at 20°C or 68°F.

Here is the AWG wire size chart in image format if you need to download it for reference.

Calculation of Wire Diameter in mm & Inch, Cross Sectional Area in mm², inch² & kcmil & Resistance from it AWG Size

Wire Diameter in millimeters “mm“.

D_n = 27 × 10^-3 × 92^(36-n)÷39

or

D_AWG = 8.251 × e^{-(0.1159) (AWG)}     …     In millimeters (mm).

Where:

• D = The wire diameter in millimeter “mm”.
• n & AWG = Number of the gauge size. 

Note: For larger gauge sizes like 4/0 (0000), 3/0 (000), 2/0 (00) & 0 (1/0), you may use the numbers for AWG as -3, -2, -1 and 0 respectively.

Wire Diameter in Inches “in”.

D_n = 5 × 10^-3 × 92^(36-n)÷39    …     In inches

Where:

• D = The wire diameter in inches “in”.
• n = Number of the gauge size. 

Wire Cross Sectional Area in Square Millimeter “mm²“.

A_n = (π ÷ 4) × D_n²

A_n = 12.668 × 10^-3 V 92^(36-n)÷19.5

Where:

• A_n = Cross sectional area of “n” gauge wire size in square millimeters “mm²“.
• n = The number “#” of gauge size.
• D = Wire square diameter in “mm²“.

Wire Cross Sectional Area in Square Inches “in²“.

A_n = (π ÷ 4) × D_n²

A_n = 19635 × 10^-6 × 92^(36-n)÷19.5

Where:

• An = Cross sectional area of “n” gauge wire size in square inches “in²“.
• n = The number “#” of gauge size.
• D = Wire square diameter in “in²“.

Wire Cross Sectional Area in kcmil “kilo circular mils”.

A_n = 1000 × D_n² = 0.025 × 92^(36-n)÷19.5

Where:

• An = cross sectional area of “n” gauge wire size in kcmil.
• kcmil = kilo circular mils.
• n = the number of gauge size.
• D = wire square diameter in in².

Note: kcmil is also known as MCM “thousands of circular mils” i.e. 1kcmil = 1MCM = 0.5067 mm².

• 2 MCM ≈ 1 mm²
• 1000 mils = 1 inch

In addition, MCM and kcmil is used for large diameter wires in AWG.

Resistance per 1000 feet at 20°C or 68°F:

R_n = 0.3048 × 10⁹ × ρ ÷ (25.4²x A_n)

Where;

• R = Resistance of the wire conductors in “Ω/kft”.
• n = # of gauge size.
• ρ = rho = resistivity in (Ω·m).
• An = the cross sectional area of n #gauge in square inches “in²“.

Resistance per 1000 Meters at 20°C or 68°F:

R_n = 10⁹ × ρ ÷ A_n

Where

• R = Resistance of the wire conductors “in Ω/km”.
• n = # of gauge size.
• ρ = rho = resistivity in (Ω·m).
• An = the cross sectional area of n #gauge in square millimeters “mm²“.

Wire Size Ampacity & Breaker Size Charts Based on AWG

Derived from the wire gauge chart and based on AWG sizes, the following fig shows the commonly used wire gauge size for different applications.

The following AWG table shows the different AWG gauges and its associated ampacities and wire applications.

Wire Gauge	Rated Ampacity	Wire Applications
4/0 (0000)	260 Amps	The largest wire size likely to be found at residential electrical installations
3/0 (000)	200 Amps	Service entrance and feeder cable
1/0 (0)	150 Amps	Service entrance and feeder cable
2 Gauge	95 Amps	Large water heater elements
4 Gauge	70 Amps	Electric furnaces, large electric heaters
6 Gauge	55 Amps	Furnaces, cooktops and electric ranges
10 Gauge	30 Amps	Electric clothes dryers, 240V window Air Conditioners, electric water heaters
12 Gauge	20 Amps	Kitchen, bathroom & outdoor receptacles (outlets) – 120V Air Conditioners
14 Gauge	15 Amps	Light fixtures, lamps, receptacles, lighting circuits
16-Gauge	13 Amps	Extension cords (light-duty)
18 Gauge	10 Amps	Low-voltage lighting and lamp cords

You may downlead the above table as a reference sheet as follow:

The following two charts shows the suitable circuit breaker sizes in Amps with wire gauge sizes and different level of voltages.

Here is the NEC table as a chart (image format to downloads as a reference)

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