Electrical Calculators
Wire Ampacity / Wire Size
Document load, conductor material, and rating assumptions.
01
Inputs
02
Result & worksheet
36.4 A usable — below entered load
The candidate conductor does not meet the entered load and limitations. Verify a larger conductor or revised installation.
Recorded summary
- Required ampacity: 50.0 A
- Adjusted table ampacity: 36.4 A
- Terminal limit: 40 A
- Usable ampacity: 36.4 A
Formula used
Required ampacity = noncontinuous load + 125% of continuous load; adjusted ampacity = table ampacity × adjustment × correctionCalculation steps
- 20 A + (1.25 × 24 A) = 50.0 A required
- 50 A × 0.8 × 0.91 = 36.4 A adjusted
- Lower of adjusted ampacity and 40 A terminal limit = 36.4 A
Assumptions
- Entered factors and temperature column are correct for the installation
- No special cable, rooftop, bundling, dwelling, motor, transformer, or equipment rule supersedes this worksheet
- The terminal limitation is entered separately
Verify before use
- NEC Article 310 ampacity table and conditions of use
- Temperature limitations at equipment terminations
- Adjustment and ambient correction rules
- Small-conductor, overcurrent-device, and equipment-specific rules
- Voltage drop and local amendments