Wire Ampacity Calculator Formula

Understand the math behind the wire ampacity calculator. Each variable explained with a worked example.

Use the Wire Ampacity Calculator

Formulas Used

Wire Area

wire_area = area_cmil

Estimated Ampacity

ampacity = area_cmil * max_density

Variables

VariableDescriptionDefault
awg_numberAWG Gauge Number14
max_densityMax Current Density(A/cmil)0.003
diameter_milsDerived value= 1000 * pow(92, (36 - awg_number) / 39) / 200calculated
area_cmilDerived value= pow(diameter_mils, 2)calculated

How It Works

Wire Ampacity

I_max = Area x Current_Density

Typical chassis wiring: 0.003 A/cmil. Always check NEC tables for installations.

Worked Example

14 AWG copper wire.

awg_number = 14max_density = 0.003
  1. 01Diameter = 64.08 mils
  2. 02Area = 4106 cmil
  3. 03Ampacity = 4106 x 0.003 = 12.3 A

Ready to run the numbers?

Open Wire Ampacity Calculator