The Motor Wire Size Calculator will calculate the proper wire size for a given motor HP and voltage. This applies to three-phase AC motors. This calculator will also give you motor amps and recommended breaker size, starter size, heater size and conduit size.

Motor Wire Size Calculator


Enter the motor horsepower and voltage.

Circuit Element Electrical Rating
Motor Wire Size: 14 AWG
Motor Amperes: 4.4 Amps
Breaker Size: 20 Amps
Starter Size: 0
Heater Amperes: 5.06 Amps
Conduit Size: ¾ Inches

Note: Always refer to NEC when sizing conduit. Breaker size should generally be 125% of FLA of motor.

A good field reference for maintenance and troubleshooting is Ugly's Electric Motor and Controls (Ugly's Electric Motors And Controls, 2014 Edition). This calculator is based on information found in this reference guide, and can help electricians troubleshoot maintenance and control circuits.

To calculate wire size for a circuit, use the Wire Size Calculator or the Advanced Wire Size Calculator. To calculate wire ampacity for a circuit, use the Wire Ampacity Calculator or the Advanced Wire Ampacity Calculator.


For long conductor runs where voltage drop may be an issue, use the Voltage Drop Calculator to determine proper conductor sizing and maximum circuit length. Visit the Tables page to view reference tables such as Maximum Ampacity for Current-Carrying Conductors.


Visit the Terms of Use and Privacy Policy for this site. Your feedback is greatly appreciated. Let us know how we can improve.