50 Amp Wire Size - Calculate Proper Wire Gauge/Thickness

50 Amp Wire Size - Calculate Proper Wire Gauge/Thickness

50 Amp is a very common current requirement we need proper wires for, especially at home, in the RVs, boats, cars, etc. While transferred power depends on the voltage applied to the circuit, energy efficiency and cable temperature depend on the wire thickness and its electrical resistance.

When calculating proper wire thickness and circuit breaker, there are a few important things to consider. But, whatever You do, safety first.

Published: April 1, 2022.

On This Page:

• AWG Wire Sizes Chart
• Calculating the Right Wire Gauge
• 50 Amps Circuit Breaker

AWG Wire Sizes Chart

The following comparison chart lists AWG wire sizes with the most important features of such wires, including the "Ampacity" - wire current carrying capacity.

AWG#	Diameter(mm/inches)	Area(mm2/in2)	Resistance (Copper)(mΩ/m;mΩ/ft)	Ampacity (A)
				@60°C/140°F	@75°C/167°F	@90°C/194°F
4/0(0000)	11.68400.4600	107.21930.1662	0.16080.04901	195	230	260
3/0(000)	10.40490.4096	85.02880.1318	0.20280.06180	165	200	225
2/0(00)	9.26580.3648	67.43090.1045	0.25570.07793	145	175	195
AWG 0 (1/0)	8.25150.3249	53.47510.0829	0.32240.09827	125	150	170
1	7.34810.2893	42.40770.0657	0.40660.1239	110	130	145
2	6.54370.2576	33.63080.0521	0.51270.1563	95	115	130
3	5.82730.2294	26.67050.0413	0.64650.1970	85	100	115
AWG 4	5.18940.2043	21.15060.0328	0.81520.2485	70	85	95
5	4.62130.1819	16.77320.0260	1.0280.3133	-	-	-
AWG 6	4.11540.1620	13.30180.0206	1.2960.3951	55	65	75
7	3.66490.1443	10.54880.0164	1.6340.4982	-	-	-
AWG 8	3.26360.1285	8.36560.0130	2.0610.6282	40	50	55
9	2.90640.1144	6.63420.0103	2.5990.7921	-	-	-
AWG 10	2.58820.1019	5.26120.0082	3.2770.9989	30	35	40
11	2.30480.0907	4.17230.0065	4.1321.260	-	-	-
AWG 12	2.05250.0808	3.30880.0051	5.2111.588	20	25	30
13	1.82780.0720	2.62400.0041	6.5712.003	-	-	-
AWG 14	1.62770.0641	2.08090.0032	8.2862.525	15	20	25
15	1.44950.0571	1.65020.0026	10.453.184	-	-	-
16	1.29080.0508	1.30870.0020	13.174.016	-	-	18
17	1.14950.0453	1.03780.0016	16.615.064	-	-	-
AWG 18	1.02370.0403	0.82300.0013	20.956.385	10	14	16
19	0.91160.0359	0.65270.0010	26.428.051	-	-	-
20	0.81180.0320	0.51760.0008	33.3110.15	5	11	-
21	0.72290.0285	0.41050.0006	42.0012.80	-	-	-
22	0.64380.0253	0.32550.0005	52.9616.14	3	7	-
23	0.57330.0226	0.25820.0004	66.7920.36	-	-	-
24	0.51060.0201	0.20470.0003	84.2225.67	2.1	3.5	-
25	0.45470.0179	0.16240.0003	106.232.37	-	-	-
26	0.40490.0159	0.12880.0002	133.940.81	1.3	2.2	-
27	0.36060.0142	0.10210.0002	168.951.47	-	-	-
28	0.32110.0126	0.08100.0001	212.964.90	0.83	1.4	-
29	0.28590.0113	0.06420.0001	268.581.84	-	-	-
30	0.25460.0100	0.05090.0001	338.6103.2	0.52	0.86	-
31	0.22680.0089	0.04040.0001	426.9130.1	-	-	-
32	0.20190.0080	0.03200.0000	538.3164.1	0.32	0.53	-
33	0.17980.0071	0.02540.0000	678.8206.9	-	-	-
34	0.16010.0063	0.02010.0000	856.0260.9	0.18	0.3	-
35	0.14260.0056	0.01600.0000	1079329.0	-	-	-
36	0.12700.0050	0.01270.0000	1361414.8	-	-	-
37	0.11310.0045	0.01000.0000	1716523.1	-	-	-
38	0.10070.0040	0.00800.0000	2164659.6	-	-	-
39	0.08970.0035	0.00630.0000	2729831.8	-	-	-
40	0.07990.0031	0.00500.0000	34411049	-	-	-

Note: Ampacities are given for enclosed wires @86°F (@30°C) ambient temperatures.

Calculating the Right Wire Gauge

When looking for the right wire thickness for 50 Amps current, first we have to find the proper wire thickness at the required temperatures as listed in the chart.

Note: Wire thickness is very often calculated for temperatures of 167°F (75°C), but 140°F (60°C) is already a hot enough temperature to prevent an adult to hold the cable with an unprotected hand for more than a few seconds. Choosing a lower temperature adds an additional safety level.

Another important requirement for 50 Amps wire size is the "80% Rule":

For example, when calculating wire size for 50 Amps circuit, we will go for the wire that features Ampacity of:

Ampacity = 50 Amps / 0.80 = 62.5 Amps

So, for a 50 Amps wire, we will choose the wire with the Ampacity of AT LEAST 62.5 Amps and the required temperature.

If we check the wire chart, we will find that there is no wire with an Ampacity value of 62.5 Amps, so we will choose the next best thing:

T = @60°C/140°F) → Ampacity = 70 Amps → AWG 4

T = @75°C/167°F → Ampacity = 65 Amps → AWG 6

T = @90°C/194°F → Ampacity = 75 Amps → AWG 6

As one can see, different maximum temperatures also mean different wire sizes - some electricians may consider AWG 4 wire an overkill for a 50 Amps current, especially if the wires are not extra long, but better safe than sorry.

So, for short, we can safely say:

50 Amps wire size → AWG 4 wire

AWG 4 wire features:

- diameter: 0.2043 inches (5.189 mm),

- area: 0.0308 inches2 (41.7 kcmil, 21.1506 mm2),

- electric resistance: 0.2485 mΩ/ft (0.8152 mΩ/m),

- Ampacity: 70 Amps @60°C/140°F, 85 Amps @75°C/167°F and 95 Amps @90°C/194°F.

Choosing thicker wires, in this example, AWG 4 instead of AWG 6, decreases energy losses and the operating temperature of the wires.

But, just note that thicker cables also require more space, they are heavier, thicker, often more difficult to work with, etc.

Note: Never, but really never use thinner cables than required - for example, don't go for AWG 8 wires (or thinner) for 50 Amp circuits.

50 Amps Circuit Breaker

When looking for a proper circuit breaker, finding proper amperage if the circuit breaker is very simple - for a 50 Amps circuit, one needs 50 Amps electric breaker.

Unlike wires, which can be somewhat thicker, for a 50 Amps circuit, one should NEVER use a stronger circuit breaker. Also, weaker electric circuit breakers may trip too often, so, they are not recommended either.

Note: if You are unsure, contact a local certified electrician for more information, including local laws and regulations.

Long Story Short: When looking for a 50 Amp wire, go for AWG 4 copper wires, especially if the cable is longer than 30 feet (~9.2m) and shorter than 100 feet (~30m).

For shorter cables, AWG 6 wire may be used, but one risks somewhat higher operating temperatures.