AWG 40 Wire
Diameter 0.0031″
Millimeters 0.079 mm
Cross-section 10 cmil
mm² 0.0049
Nominal bare-conductor dimensions per ASTM B258. AWG is geometric: d = 0.005 × 92(36−n)/39 in with n = 40; area is derived from the diameter. Ampacity depends on insulation, bundling, and the electrical code in force — it is a property of the installation, not the gauge.