Wire Ampacity Calculator Formula
Understand the math behind the wire ampacity calculator. Each variable explained with a worked example.
Formulas Used
Wire Area
wire_area = area_cmilEstimated Ampacity
ampacity = area_cmil * max_densityVariables
| Variable | Description | Default |
|---|---|---|
awg_number | AWG Gauge Number | 14 |
max_density | Max Current Density(A/cmil) | 0.003 |
diameter_mils | Derived value= 1000 * pow(92, (36 - awg_number) / 39) / 200 | calculated |
area_cmil | Derived 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
- 01Diameter = 64.08 mils
- 02Area = 4106 cmil
- 03Ampacity = 4106 x 0.003 = 12.3 A
Frequently Asked Questions
What affects ampacity?
Wire gauge, insulation type, ambient temperature, and bundling.
Is this NEC rated?
No. NEC ratings depend on specific conditions. This is an engineering estimate.
What happens if exceeded?
Wire overheats, insulation degrades, fire risk increases.
Ready to run the numbers?
Open Wire Ampacity Calculator