Convert AWG to mm².

AWG is a logarithmic sizing scale: each step is a fixed ratio in diameter, not a fixed step in area. Smaller AWG number means thicker wire. Sizes larger than 1 AWG are written 1/0 (one aught), 2/0, up to 4/0.

Formula

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

n = AWG number  (use n = −3 for 4/0, n = −2 for 3/0, n = −1 for 2/0, n = 0 for 1/0)

Per ASTM B258. The 0.127 mm coefficient is 0.005 inch × 25.4. The formula gives the bare-conductor diameter; cross-sectional area is computed from that.

Reference values

"Next IEC standard size up" is the next-larger size in IEC 60228 (the standard for conductors of insulated cables): 0.5, 0.75, 1.0, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240 mm². When sourcing in metric to replace AWG, round UP — never down — to maintain ampacity. For AWG sizes below 0.5 mm², IEC 60228 does not define a standard size; specify by mm² directly.

Things to watch for

• AWG ≠ standard metric. The IEC standard sizes (1.5, 2.5, 4, 6, 10, 16 mm² ...) don't align exactly with any AWG size. 14 AWG is 2.08 mm² but you'll usually order 2.5 mm² in metric — the next standard size up.
• Round up when substituting. If you're replacing AWG wire with metric in an existing design, the metric wire must be at least as large in cross-section. Rounding down can violate ampacity.
• NEC and IEC ampacity differ. The same physical wire has different rated ampacity under NEC vs IEC because the calculation method, ambient temperature reference, and installation assumptions differ. Always size to the local code's tables, not by direct cross-reference.
• Stranded wire has lower effective area. A stranded conductor of nominal 2.5 mm² area uses smaller strands with gaps, so its actual copper area is slightly less than a solid 2.5 mm². For low-voltage signal wiring this doesn't matter; for high-current power runs, check the manufacturer datasheet.
• 4/0 is roughly 107 mm² but not equal to it. The closest IEC standard is 120 mm². For very large feeders, you'll often see both expressed (e.g. "750 kcmil = ~380 mm²").

What is a American Wire Gauge?

AWG is a logarithmic wire-size scale defined by ASTM B258. The diameter formula is d = 0.005 × 92^((36−n)/39) in. Smaller AWG numbers mean thicker wire. Electrical wire sizing in the US, Canada, and parts of Latin America.

What is a square millimeter?

A unit of cross-sectional area equal to one millimeter by one millimeter, used to specify wire conductor size in IEC standards. Electrical wire sizing in most countries outside North America, per IEC 60228.

How to convert American Wire Gauge to square millimeter

To convert a value from American Wire Gauge (AWG) to square millimeter (mm²), apply the conversion factor shown in the formula above. The calculation is the same whether you do it by hand, in a spreadsheet, or with the live converter on this page.

Steps:

1. Take your input value in AWG.
2. Apply the formula d (mm) = 0.127 × 92^((36 − n) / 39) A (mm²) = π × (d / 2)² n = AWG number (use n = −3 for 4/0, n = −2 for 3/0, n = −1 for 2/0, n = 0 for 1/0).
3. The result is your value in mm².

For repeated calculations, save the formula in a spreadsheet or use the live converter at the top of this page — it handles the math automatically and displays the result as you type.

Frequently asked questions

How do I convert AWG to mm²?

Apply the formula AWG → mm² shown above, or just type your value into the converter at the top of this page. The result updates instantly.

Which is bigger, AWG or mm²?

This depends on the conversion ratio in the formula. If the factor multiplied by your value gives a larger number, then mm² is the smaller unit (so it takes more of them to express the same quantity). If the result is smaller, then mm² is the larger unit.

When would I use AWG versus mm²?

Both units measure electrical, so the choice depends on context. American wire gauge is typically used for wiring specifications and equipment ratings; square millimeter similarly. Most professional fields standardize on one or the other based on regional conventions or technical tradition.

How precise is this AWG to mm² conversion?

The conversion factor shown is the internationally defined exact value (or the best-published approximation if the relationship is irrational, like degrees-to-radians). The live converter on this page uses double-precision floating-point math, accurate to about 15 significant digits — far beyond any practical engineering need.

Is the conversion ratio exact, or an approximation?

Most unit conversions between SI metric units, and between SI and US customary units, have been formally defined as exact values since the 1959 international yard-pound agreement and subsequent SI redefinitions. Exceptions are unit pairs that involve irrational numbers (radians, e.g.) or empirical conversions (like food calories, which depend on temperature). When in doubt, consult the formula at the top of this page.

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See also