How To Tell What Gauge Wire Is: Learn Different Methods to Calculate It

The gauge of the wire tells how much electrical current a wire can carry without heating up.

Suppose you accidentally pass a current higher than a particular wire gauge’s rated current carrying capacity.

The electrical wiring may heat up and generate heat leading to wire deterioration. It may further affect its insulation which may cause an electrical fire.

Then, how to tell what gauge wire is?

There are two ways. Let’s get into the details of both methods.

Gauging Round Solid Wire With a Wire Stripper:

Get yourself a wire gauging tool. 

Wire gauging tools are basically a piece of metal (usually rectangular or circular) studded with numerous holes around its perimeter. Each hole has a label that corresponds to a certain gauge size. 

• You can buy a wire gauging tool at a home supply store or local hardware store.
• Ensure your gauge tool specifies the measurement system it corresponds with. If you’re in North America, your gauging tool will probably measure according to the AWG scale.

The next step is estimating the gauge size of your wire. 

Estimate the approximate size of your wire and try to determine the gauge holes that are the same size. Doing so will save you time because you’ll avoid the hassle of having to fit your wire into excessively large or small holes on the scale. 

Caption: Illustration of Wire Gauging Tool

Now, slide the wire into the approximate gauges and see where it fits. 

Put the wire into every approximate gauge until you find the perfect gauge. The wire corresponds to the smallest gauge it can fit into. The fit should be tight but not excessively snug.

• Keep in mind every gauge will have a slightly larger gauge next to it. Don’t use such holes to measure the gauge size. Such gauges are there in order to enable you to easily remove the wire from the hole.

It’s best to compare your wire to another wire that you know the gauge. 

If you don’t have access to a wire gauging tool, you can attempt to determine the gauge of your wire by comparing it to another with a predetermined gauge size. For instance, if you have a wire with a small diameter, you can compare it to a wire of gauge 22, 21, and 20 to see which is closest.

• If you don’t have any wires with a predetermined gauge size, you can always go to a local hardware store for further assistance. If they don’t have a wire gauging tool, they will probably have a variety of wires with a predetermined gauge that you can use to compare your wire with.

Caption: wire strippers

Gauging Stranded Wire By Measuring Cross-section

Measure the diameter of a single wire. 

A stranded wire consists of numerous thin wires twisted together to form a single wire. In order to calculate the gauge of a stranded wire, you’ll need to determine the diameter of a single wire strand in inches or multimeters.

• If your wire has a very small diameter (very large gauge) and you can’t measure it using a ruler, use a wire and conduit measuring device. You can get this tool at most hardware stores.

Next, multiply the diameter of your wire by itself. 

If the diameter of your wire was 0.0005 inches, multiply the value by itself. You’ll need to count the individual strands and then multiply the stranded wire diameter by the number of strands. For instance, if your wire has 20 strands, multiply the value by 0.0005.

• The result will give you the CMA (Circular Mils) value for your stranded wire. This is another popularly used wire gauge scale that calculates the circular area of a wire. 
• As a general rule, smaller diameter wires (large gauge) contain fewer strands. Wires with a smaller diameter may have seven or eight strands. On the other hand, larger diameter wires (smaller gauge) might have as much as 30. 40 or 100 strands.

Determine your wire’s corresponding AWG size. 

Once you determine the CMA of your stranded wire, check online to determine the corresponding AWG size. Also, you could simply visit a local hardware store that often has a hardcopy gauge comparison table.

• For instance, if the diameter of your wire strand is 0.005 inches and your stranded wire has 20 strands, then the corresponding CMA will be 525 with a 22 AWG. 

Wire Gauge Reference Table (AWG)

AWG	Diameter (MM)	Diameter (Inches)	SWG	BWG	Circular Mils
36 AWG	0.12700	0.005000	39	35	24.999282
34 AWG	0.16002	0.006300	37	34	39.688860
32 AWG	0.20320	0.008000	35	33	63.998162
30 AWG	0.25400	0.010000	33	31	99.997128
28 AWG	0.32004	0.012600	30	29	158.755440
26 AWG	0.40386	0.015900	27	27	252.802739
24 AWG	0.51054	0.020100	25	25	403.998397
22 AWG	0.64262	0.025300	23	23	640.071617
20 AWG	0.81280	0.032000	21	21	1023.970591
18 AWG	1.02362	0.040300	19	20	1624.043356
16 AWG	1.29032	0.050800	18	18	2580.565884
14 AWG	1.62814	0.064100	16	16	4108.691995
12 AWG	2.05232	0.080800	14	14	10383.311783
10 AWG	2.58826	0.101900	12	12	16511.775768
8 AWG	3.26390	0.128500	10	10	26250.698587
6 AWG	4.11538	0.162023	7	8	41614.804788
4 AWG	5.18160	0.204000	5	6	66562.088282
2 AWG	6.55320	0.258000	2	3	1333075.217970
2/0 AWG	9.26592	0.364800	2/0	2/0	167767.341584
3/0 AWG	10.40384	0.409600	3/0	3/0	211593.922848
4/0 AWG	11.68400	0.460000	4/0	4/0	211593.922848
5/0 AWG	13.11910	0.516500	7/0	—	266764.588301
6/0 AWG	14.73200	0.580000	—	—	336390.338592

• SWG – refers to the Sterling or Standard Wire gauge
• BWG –  refers to the British Wire Gauge (old British system used in the past)

Caption: voltage tester

Conclusion:

Determining wire gauges requires minimal equipment, which works virtually for all wires and cables.

The cables are the main functional component of any electrical device.

Always look for high quality and the right gauge.

Wiringo is the world’s leading manufacturer of top-quality wiring harnesses and customized cable assemblies, which you get after the toughest quality assurance tests.