AWG defines diameter; mm² defines area. They never convert exactly, so a terminal should be selected by its published wire range — not by the number printed on the wire. Terminal drawings circulate in both systems, and one project can carry both at once: equipment designed in North America arrives with AWG specifications, while the cable and the terminal barrel are ordered in mm². The two numbers look interchangeable, and they are not. What AWG and mm² Actually Describe AWG, the American Wire Gauge, describes the diameter of a solid round conductor on a logarithmic scale. The scale runs backwards: a larger AWG number means a thinner conductor, and every six gauge steps the cross-sectional area halves. The metric system describes the conductor's cross-sectional area directly, in square millimetres. IEC 60228 fixes the standard sizes that equipment is designed around: 0.5, 0.75, 1.0, 1.5, 2.5, 4, 6, 10, 16, 25, 35 mm² and above. Because one system defines a diameter and the other an area, conversions land between the metric sizes. For reference, the AWG diameter follows d = 0.127 × 92((36 − AWG) / 39) mm, and the area is A = π × d² / 4. Common AWG to mm² Equivalents for Terminals The table below covers the range used by most control, harness and panel terminals. AWG Conductor diameter (mm) Actual area (mm²) Nearest IEC 60228 size (mm²) 20 0.812 0.518 0.5 18 1.024 0.823 0.75 17 1.150 1.04 1.0 16 1.291 1.31 1.5 14 1.628 2.08 2.5 12 2.053 3.31 4 10 2.588 5.26 6 8 3.264 8.37 10 6 4.115 13.3 16 4 5.189 21.2 25 2 6.544 33.6 35 Values are for solid round copper conductors at 20 °C, calculated from the AWG defining formula (ASTM B258). The final column is the nearest IEC 60228 standard cross-section by area and is given only to help read drawings that use the other system. Why the Difference Matters When You Select a Terminal A terminal data sheet publishes a wire range in one or both systems — for example, 22–16 AWG / 0.5–1.5 mm². That range is the capacity window of the crimp barrel, and the conductor has to land inside it. Four problems recur: Rounding the conductor down. 18 AWG is 0.823 mm², so a barrel rated 0.5–0.75 mm² will not close correctly around it, even though 18 AWG is sometimes written casually as "0.75". Forcing an oversized conductor. A conductor above the barrel's maximum leaves strands outside the crimp. That is a reliability problem, not a fit problem. Using the wrong die. Crimping tools are rated by cross-section, not by AWG number. A die designed for 0.5–1.0 mm² will not produce a correct crimp on a 2.5 mm² conductor. Reading the insulation colour. Colour conventions are not universal between AWG and metric product families, and twin or high-temperature versions may carry a different marking. Conductor class matters as well. A fine-stranded conductor behaves differently from a solid conductor of the same nominal area, and in a screw or spring clamp it is normally terminated with a wire ferrule rather than clamped bare. A Three-Step Check Before You Order Record the conductor's actual cross-section and class from the cable data sheet, in both AWG and mm² where possible. Compare the converted area with the terminal's published minimum and maximum. If the conductor sits between two nominal sizes, choose the terminal whose range contains it — never shrink the barrel to meet a rounded-down number. Confirm the crimping die covers the same cross-section range, then crimp a sample and inspect the joint before committing to a batch. If a project mixes AWG and mm², fix one system as the drawing reference and convert the other into it. Frequently Asked Questions Q: Is 16 AWG the same as 1.5 mm²? A: No. 16 AWG is 1.31 mm². 1.5 mm² is the nearest IEC 60228 standard size, but the two are not the same conductor. Select the terminal against its published wire range, not a rounded metric label. Q: Why do AWG and mm² never convert to round numbers? A: AWG is defined by conductor diameter on a logarithmic scale; mm² is defined by cross-sectional area. The two were standardised independently, so exact conversions land between the metric sizes. Q: Should I round up or down when converting a conductor size? A: Never round a conductor down to fit a smaller barrel. Convert to the actual area, then check it against the terminal's published minimum and maximum. Q: Does a terminal data sheet always list both AWG and mm²? A: Not always. Where only one system appears, convert the conductor and confirm it against the range that is published. Talk to KF Terminals Send us the conductor size and class, the terminal type and the application. We will confirm the matching part number and wire range from the product data sheet. Start from non-insulated terminals, cord end terminals (wire ferrules) or copper tubular lugs, and check crimping tools and accessories for the matching die. You can also read how butt splice connectors handle different wire gauges, or send your requirements directly. References: ASTM B258 (AWG sizes of solid round copper wire) and IEC 60228 (standard metric conductor cross-sections). Conversion values are calculated from the AWG defining formula. Always confirm the wire range published for the specific terminal part number. 0