NEC 430 "Interpolated HP" Calculator

Per NEC 430.6(A), if a motor is marked in amperes, but not horsepower, we must use Tables 430.247–430.250 to find or interpolate an assumed HP.

Instructions:

  1. Select the NEC table relevant to your motor type (single‐phase, DC, etc.).
  2. Select the voltage column from that table.
  3. Enter the motor's nameplate amps (when no HP is listed).
  4. Click "Calculate HP." The tool will interpolate if needed.

Note: The table values here are from the 2023 NEC. Double‐check your exact code edition. If your amps lie outside the smallest/largest row in the table, this tool will advise consulting the manufacturer or using engineering judgment.