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Wire Gauge Converter

Convert any wire size between AWG, mm², SWG, kcmil and diameter. Not sure what you've got? Measure the bare conductor with calipers, solid or stranded, to find its true size and check it isn't smaller than the label claims.

Convert a size

For AWG you can type 4/0, 0000, 2/0 or a number like 12.

Measure your cable

How to measure accurately
  • Switch the power off first. Strip a short length of insulation and measure the bare metal, never over the insulation.
  • Use digital calipers or a micrometer. Measure twice, turning the wire a quarter turn, and use the average.
  • Stranded cable: the most accurate way is to count the strands and measure one strand. Measuring the whole bundle only gives an estimate, because of the gaps between strands.
  • Fine flexible cable (welding, battery, car audio) can have hundreds of strands: count the strands in a small group and multiply.

Size charts

AWG, mm² and SWG explained

  • mm² is the conductor's cross-section area, used in the UK and Europe (1.5 mm² lighting cable, 2.5 mm² sockets).
  • AWG (American Wire Gauge) goes backwards: a smaller number is a thicker wire. Every 3 gauges halves or doubles the area, and every 6 gauges halves or doubles the diameter. Above 1 AWG come 1/0, 2/0, 3/0 and 4/0, then kcmil (thousands of circular mils).
  • SWG (Standard Wire Gauge) is an older British scale, still used for fuse wire, welding wire and craft wire.
  • Standard metric and AWG sizes don't line up exactly. When swapping, choose the next size up, never down.

Undersized cable is common

  • Cheap cables, extension leads, solar, car audio and "battery" cables are often thinner than their label, or made of copper-clad aluminium (CCA), which looks silver when cut or scraped.
  • Car audio and some import cables are labelled in "gauge" but measured over thick insulation: a "4 gauge" kit may really be 8 AWG.
  • A cable more than about 5% smaller than claimed carries less current and drops more voltage than you've planned for. Size your run with the Cable Size Calculator.

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