AWG Wire Size Chart & Calculator

Look up any American Wire Gauge — diameter, area, resistance and amp rating — convert AWG to mm² and mm, find the gauge for a given current, and compare it with SWG.

Pick a gauge to see every spec at once, type a current to get the smallest wire that carries it, or convert between AWG, mm² and mm. The full chart below is a real, selectable table — not an image — with both amp-rating columns and copper resistance for DC, 12 V and electronics work.

Amp ratings are a general reference for low-voltage/DC and electronics work (from the chassis-wiring and power-transmission chart in the Handbook of Electronic Tables and Formulas), not a substitute for an electrician on mains or building wiring. Resistance and dimensions are computed from the AWG formula for annealed copper or aluminum at 20 °C.

Sizing a real run? Compute resistance at any length and temperature with the wire resistance calculator, check losses with the voltage drop calculator, find the current for a load with the Ohm's Law Calculator, or for solar and battery wiring use the Off-Grid Solar Calculator and solar wire size calculator.

AWG wire size chart

This is the full American wire gauge chart from 4/0 (0000) down to 40 AWG — an electrical wire gauge chart you can read for the thickness (the conductor diameter), the area, the resistance and the amperage each gauge can carry. Every six gauges the diameter doubles, and every three gauges the cross-sectional area doubles. Scroll the table sideways on a phone; tap a row to highlight it.

American wire gauge size, diameter, area, resistance and amp-rating chart (copper).
AWG Dia. (mm) Dia. (in) Area (mm²) Circular mils Ω / 1000 ft Ω / km Chassis (A) Power tx (A)

AWG to mm² / mm conversion

Wire diameter follows a fixed formula, so this works as an AWG to mm² converter both ways — AWG to mm2 (written mm²) and mm² to AWG — as well as wire gauge to mm by diameter. For diameter in inches the rule is d = 0.005 × 92(36−n)/39; in millimetres it is d = 0.127 × 92(36−n)/39. Cross-sectional area is π(d/2)².

d(mm) = 0.127 × 92^((36 − n) / 39) · area(mm²) = π × (d/2)²

Pick a gauge in the converter and it groups the area, diameter and circular mils together; the common sizes people look up most are 14 AWG (about 2.08 mm²), 12 AWG in mm² (about 3.31 mm²) and 16 AWG (about 1.31 mm²). For the 0, 00, 000 and 0000 gauges, n is 0, −1, −2 and −3. Real cable is sold in standard metric sizes, so 12 AWG (3.31 mm²) is bought as 2.5 mm², and 10 AWG (5.26 mm²) as 6 mm². The converter above does AWG ↔ mm² ↔ mm in both directions. To compute resistance for an arbitrary length or temperature from that area, use the wire resistance calculator.

Wire gauge amp rating (chassis vs power transmission)

The chart gives two amp numbers per gauge, and choosing the wrong one is the single most common mistake people make with a wire gauge amp chart:

  • Chassis wiring — a single wire alone in open air. It sheds heat freely, so it carries more current. Think of a jumper inside an enclosure.
  • Power transmission — the wire bundled with others, where heat is trapped. It uses the very conservative 700-circular-mils-per-amp rule, giving a much lower figure. This is the column to use for any normal multi-conductor cable.

So 22 AWG reads about 7 A as chassis wiring but only ~0.92 A bundled — same wire, different cooling. When in doubt, use the power-transmission number.

Resistance per AWG gauge

Resistance comes from the conductor's area and the metal's resistivity: R per metre = ρ ÷ area, with ρ = 1.724×10−8 Ω·m for annealed copper and 2.82×10−8 for aluminum. Aluminum has roughly 1.6× the resistance of copper for the same gauge, which is why an aluminum run needs a size or two larger. The chart shows copper ohms per 1000 ft and per km; switch the lookup to aluminum for those figures.

SWG to AWG conversion

The British Standard Wire Gauge (SWG) is a different scale from AWG, so the numbers are not interchangeable. SWG diameters are fixed values from BS 3737; the converter finds the closest AWG for any SWG size. A few common comparisons:

SWGSWG dia. (mm)Closest AWG

12 V DC & automotive wire gauge

Automotive, RV, marine and 12 V solar wiring lives in this chart's sweet spot: low-voltage DC at fairly high current. At 12 V a device drawing 120 W pulls 10 A, and a small inverter can pull 80–100 A, so cable that looks oversized is normal. Two things matter most for 12 V: the wire must carry the current without overheating (use the power-transmission column for bundled looms), and on anything but a short run, voltage drop — not amps — usually decides the gauge. Size by current here, then confirm the run length with the voltage drop calculator.

Frequently asked questions

What amp rating is 14, 12 and 10 gauge wire?

On the electronics-handbook chart this tool uses, a single copper wire in free air (chassis wiring) handles about 32 A for 14 AWG, 41 A for 12 AWG and 55 A for 10 AWG. Bundled in a cable (power transmission) the conservative figures drop to roughly 5.9 A, 9.3 A and 15 A. Use the lower number for cables with several conductors together.

What is 12 AWG in mm²?

12 AWG is about 3.31 mm² in cross-section, with a conductor diameter near 2.05 mm. It is usually sold as the nearest metric size, 2.5 mm². For comparison, 14 AWG is about 2.08 mm² and 10 AWG is about 5.26 mm² (sold as 6 mm²).

Is AWG the same as mm²?

No — AWG is a gauge number and mm² is an actual cross-sectional area, so they measure the same wire two different ways. The converter above turns any AWG into its mm², diameter and circular mils, and goes mm² to AWG in reverse. The converted area rarely lands on a stocked size (12 AWG is 3.31 mm², not a tidy 3 or 4), so cable is bought at the nearest standard metric size above it.

Chassis vs power-transmission — which rating do I use?

Chassis wiring is a single wire alone in free air, so it carries more current; power transmission assumes the wire is bundled with others where heat builds up, using the conservative 700-circular-mils-per-amp rule. For a normal cable with several conductors, use the power-transmission column.

How do I pick a wire gauge for a given current?

Enter your current in the gauge finder above and choose chassis or power transmission; it returns the smallest gauge that covers it. On long DC runs, voltage drop usually forces a thicker wire than the amp rating alone, so check the voltage drop calculator with your actual run length before buying.

Is AWG the same as SWG?

No. AWG is the American Wire Gauge; SWG is the British Standard Wire Gauge, and the same number means different diameters. 18 AWG is about 1.02 mm while 18 SWG is 1.22 mm. The converter above lines them up so you can find the closest AWG for any SWG size.

What is the resistance of a wire per foot?

Divide the per-1000-ft value in the chart by 1000. For example, 12 AWG copper is about 1.59 Ω per 1000 ft, or roughly 0.0016 Ω per foot. Resistance scales with length and inversely with area, so doubling the length doubles the resistance and going up three gauges roughly halves it.