12 AWG has a cross-section of 3.31 mm² and a diameter of 2.053 mm. Copper resistance is about 5.21 Ω per kilometer at 20 °C.
Carregando ferramenta… / Loading tool…
Convert AWG wire gauge to mm² and diameter, or mm² to AWG, with the exact formula, a 0000 to 40 chart and copper resistance per meter
AWG (American Wire Gauge) is a logarithmic scale: the higher the number, the thinner the wire. It is defined by two points, 36 AWG at 0.127 mm diameter and 0000 AWG at 0.46 in (11.684 mm), and a constant ratio between gauges: the diameter of n AWG is 0.127 mm × 92^((36 − n) ÷ 39). The cross-section is the area of the circle, π/4 × d². So 12 AWG is 2.053 mm in diameter and 3.31 mm², 14 AWG is 1.628 mm and 2.08 mm², and 10 AWG is 2.588 mm and 5.26 mm². The gauges 00, 000 and 0000 (2/0, 3/0 and 4/0) continue the count backwards as −1, −2 and −3. The tool uses the exact formula instead of a rounded chart, converts both ways, and shows copper resistance at 20 °C and the nearest standard metric size.
Between 36 AWG and 0000 AWG there are 39 steps, and the diameter grows by a factor of 92 (11.684 ÷ 0.127 = 92). Each step multiplies the diameter by 92^(1/39), about 1.123, and the area by that value squared, about 1.261. That is why every 6 gauges the diameter nearly doubles (1.123⁶ ≈ 2.0) and every 3 gauges the area nearly doubles (1.261³ ≈ 2.0). It is the rule of thumb: going from 14 AWG (2.08 mm²) to 11 AWG takes the area past 4 mm².
Resistance follows from the area. For copper at 100% IACS, with a conductivity of 58.0 MS/m at 20 °C, R = L ÷ (58.0 × 10⁶ × A). At 10 AWG that gives 3.277 Ω per kilometer; at 14 AWG, 8.286 Ω/km; at 22 AWG, 52.96 Ω/km. Real resistance changes with temperature and alloy, and stranded wire has slightly more because of the lay of the strands.
Installation cables usually follow standardized sizes: 0.5, 0.75, 1, 1.5, 2.5, 4, 6, 10, 16, 25 mm² and so on (the IEC 60228 series). AWG is continuous on a logarithmic scale, so it almost never lines up. A 2.5 mm² cross-section corresponds to 13.2 AWG: it falls between 13 AWG (2.62 mm²) and 14 AWG (2.08 mm²). 4 mm² is 11.2 AWG, 6 mm² is 9.4 AWG and 1 mm² is 17.2 AWG.
That is why the tool shows the exact value with decimals and the two neighboring gauges, and leaves the choice to someone who knows the application. It does not give current capacity: a cable's ampacity depends on the code, the insulation, the ambient temperature and the installation method, and cannot be read from the gauge alone.
Paste the code into your HTML and the tool shows up on your page, without J-Kit's navigation and ads. It still runs in the browser of whoever visits your site.
<iframe
src="https://jkit.tools/embed/en-US/awg-to-mm2-converter"
width="100%"
height="600"
style="border:0"
loading="lazy"
title="AWG to mm² Converter"
></iframe>
<p style="font-size:12px;margin:6px 0 0">Tool by <a href="https://jkit.tools/en/tools/awg-to-mm2-converter">J-Kit</a></p>Using it in a paper, class or post? Copy the link or a ready-made reference. The access date is today's.
<a href="https://jkit.tools/en/tools/awg-to-mm2-converter">AWG to mm² Converter</a>
These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.
12 AWG has a cross-section of 3.31 mm² and a diameter of 2.053 mm. Copper resistance is about 5.21 Ω per kilometer at 20 °C.
AWG and metric sizes are different scales: there is no exact equivalence. For installation cable, your project's cross-section and code are what count.
The math runs in your browser; no value is sent to a server. The tool does not give current capacity (ampacity), which depends on the code and the installation.