How to Determine Wire Sizes for Stranded Copper Wire

Updated February 21, 2017

Wire gauge size is measured and described in two different ways: American Wire Gauge and Metric Wire Gauge. American Wire Gauge is measured in inches per diameter of the wire; Metric Wire Gauge is measured in millimetres per diameter. The American formula below can easily be converted to metric gauge.

Strip 1/2 inch off the end of a copper strand wire. Twist the wire together in your fingers so that all of the strands become braided together.

Measure the end diameter of the twisted copper wire strands with a regular ruler. Better yet, use a wire gauge ruler to measure the diameter of the twisted strands. Twisted copper strands can literally be inserted into the holes of a wire gauge ruler. The precise size can be determined depending on what size hole the wire fits into.

Compare the size of the wire diameter to a wire gauge sizing chart. For example, a wire diameter of 1/4 inch will be a #2 gauge wire. A wire that measures 1/10 of an inch will be a #10 gauge wire.


A fast and easy-to-use wire gauge chart can be found on the Internet by punching in "wire gauge table" into any search engine.

Things You'll Need

  • Wire stripper
  • Ruler or wire gauge ruler
  • Wire gauge sizing chart
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About the Author

Dale Yalanovsky has been writing professionally since 1978. He has been published in "Woman's Day," "New Home Journal" and on many do-it-yourself websites. He specializes in do-it-yourself projects, household and auto maintenance and property management. Yalanovsky also writes a bimonthly column that provides home improvement advice.