What is Full-Load Amps (FLA)?

FLA is the current a motor draws at its rated horsepower, voltage, and frequency under full mechanical load. NEC Tables 430.248 (single-phase) and 430.250 (three-phase) list standard FLA values used for circuit sizing, not the nameplate current.

Why does NEC use table values instead of nameplate FLA?

NEC table values are conservative design values used to size protective devices and conductors. They are often higher than actual nameplate FLA to account for motor variation and ensure safe circuit sizing.

How do I size a breaker from the FLA result?

Per NEC 430.52, multiply FLA by 250% for an inverse-time breaker (non-time-delay). Round up to the next standard breaker size. For example, 10 A FLA × 2.5 = 25 A breaker.

How do I size the branch-circuit conductor?

Per NEC 430.22, the branch-circuit conductor must be rated at least 125% of the motor FLA. For 10 A FLA: 10 × 1.25 = 12.5 A minimum — select 14 AWG (15 A) or 12 AWG (20 A) conductor.

What if my horsepower is not in the NEC table?

This calculator interpolates linearly between adjacent NEC table entries. For accurate design, verify against the actual NEC table and consult a licensed electrician for non-standard ratings.

Does this cover DC motors or wound-rotor motors?

No. This tool covers standard AC induction motors per NEC 430.248 (single-phase) and 430.250 (three-phase). DC motors and wound-rotor motors have separate NEC tables (430.247, 430.249).

Motor Full-Load Amps Calculator

Name: Motor Full-Load Amps Calculator
Availability: InStock
Author: Nham Vu

Enter motor horsepower, voltage, and phase to get NEC full-load amperage per Table 430.248/250.

Motor Parameters

Motor Phase

Single-Phase Three-Phase

Voltage (V)

Horsepower (HP)

Results

Enter motor parameters and click Calculate.

Summary

Enter motor horsepower, voltage, and phase to get NEC full-load amperage per Table 430.248/250.

How it works

Select single-phase or three-phase motor type.
Choose the rated voltage from the dropdown (e.g. 115V, 230V, 460V).
Enter the motor horsepower rating.
The calculator looks up or interpolates the NEC FLA value.
Use the result to size breakers, conductors, and overload relays per NEC Article 430.

Use cases

Size branch-circuit breakers and fuses per NEC 430.52.
Select wire gauge using the 125% conductor rule (NEC 430.22).
Set overload relay trip current on motor starters.
Verify motor nameplate FLA against NEC table values.
Calculate service-entrance load for multiple motors.
Design control panels requiring accurate current ratings.
Check motor current draw during energy audits.
Pre-fill permit applications that require NEC FLA values.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu