How to Calculate Wire Gauge Converter
What is Wire Gauge Converter?
The Wire Gauge Converter translates between four electrical wire sizing systems: AWG (American Wire Gauge, used in US/Canada/Mexico), SWG (Standard Wire Gauge, traditional British), mm diameter (continental European, scientific), and mm² cross-section (modern international standard, used in electrical codes globally). The calculator also displays maximum ampacity (current capacity in amps) and categorizes wire by typical use case (signal, low voltage, residential, heavy duty, industrial).
Formula
- D
- Diameter (mm) — Wire diameter, measured across
- A
- Cross-section Area (mm²) — Conducting area; primary ampacity factor
Step-by-Step Guide
- 1Enter wire value in any of the 4 systems
- 2Calculator finds closest match in standard wire reference table
- 3Outputs equivalent AWG, SWG, mm diameter, mm² cross-section, and max amperage
- 4AWG is logarithmic: each increment of 6 doubles the cross-section
- 5Color codes ampacity category for safety reference
Worked Examples
Common Mistakes to Avoid
- ✕Confusing AWG (smaller number = larger wire) with metric (larger number = larger wire)
- ✕Using chassis ampacity for power transmission — power transmission ampacity is lower
- ✕Ignoring length-based voltage drop — longer wires need larger gauges
- ✕Mixing solid vs stranded ampacity ratings without checking codes
Frequently Asked Questions
Why smaller AWG = larger wire?
AWG comes from the number of die-passes used to draw wire to size — more passes means thinner wire. AWG 36 needed 36 draws (very thin); AWG 0 was undrawn (thick). The system is logarithmic with base 92^(1/39), giving each 3-step decrement ~doubled cross-section.
Is AWG 14 or 12 better for 20A circuits?
AWG 12 is safer at 20A. US code requires AWG 14 for 15A circuits, AWG 12 for 20A circuits. Use the larger wire if uncertain — bigger gauge handles higher current with less voltage drop and heat.
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