Wire Current Capacity (Ampacity) Guide
Ampacity is the maximum continuous current a conductor can carry before its temperature exceeds the rating of its insulation. In automotive design, this is rarely a static number.
A wire's capacity is governed by its cross-sectional area (gauge), the ambient temperature of its environment, and how densely it is packed with other wires (bundle derating).
Ampacity Derating Calculator
Note: This is a simplified educational tool based on SAE guidelines for 125°C XLPE wire. Always verify with specific wire manufacturer datasheets.
The Danger of Bundle Heat
When wires are bundled together in loom or tape, the inner wires cannot dissipate resistive heat into the air. If multiple wires in a bundle are carrying high current simultaneously, the core temperature of the bundle can easily exceed the insulation rating, leading to a thermal breakdown and a dead short to neighboring wires.