What is motor FLA and why does it matter?

FLA (Full Load Amps) is the current a motor draws when running at its rated horsepower and voltage. It matters because it determines your wire gauge, circuit breaker size, and overload relay settings. Undersize any of these and you risk tripped breakers, melted wiring, or fire. Oversize them and the motor has no protection against overload damage.

Why does the table FLA differ from the motor nameplate?

The table lists one current for every motor of a horsepower row and rated voltage; the nameplate shows the figure for that one motor. A Baldor L1430T, 5 HP at 230 V single-phase, prints 20.6 A against the table's 28 A. Conductors and short-circuit protection are sized from the table current; overload protection is set from the nameplate full-load amps.

How do I use FLA to select a circuit breaker?

Per NEC Table 430.52, the maximum branch-circuit protective device for motor circuits depends on the device type: 250% of FLA for inverse-time breakers, 800% for instantaneous-trip breakers, 300% for non-time-delay fuses, and 175% for dual-element time-delay fuses. These higher settings accommodate the motor's starting inrush current without nuisance tripping. A 10A FLA motor with an inverse-time breaker may therefore take a breaker as large as 25A. These percentages are ceilings, not required sizes. Always verify against NEC Article 430.52 for the specific device type and motor application. Cited to NEC Table 430.52. The code text itself is not freely available to link; confirm the figure against the current edition or your authority having jurisdiction before acting.

Does motor efficiency change the table FLA?

No. The table current depends only on the horsepower row, the rated voltage and the phase, so this page asks for no efficiency or power factor. A motor of the same rating can draw less than the table figure, and its nameplate shows by how much. For motors running many hours per day, the efficiency difference shows up on your electric bill; use our kWh calculator to estimate the cost.

Motor FLA Calculator - NEC 430 Single & 3-Phase

5 min read

Look up the full-load current (FLA) of an AC motor from the printed motor table. Pick single-phase or three-phase, the rated voltage and the horsepower row, and the page gives the table current and the conductor figure that follows from it.

Electric motor cross-section with nameplate data sheet showing FLA readings.

Where the Full-Load Current Comes From

The result is a printed table cell, not a formula. The motor table lists one full-load current for each horsepower row at each rated voltage: single-phase at 115 V and 230 V, three-phase at 208 V, 230 V, 460 V and 575 V. The cells on this page are the ones Mersen reprints in its motor fuse selection tables, whose footnote reads "Values obtained from NEC 2017 Table 430.250". Mersen and Eaton print the same three-phase figures in the 208 V column, and we have not opened NFPA's own text of Table 430.250, so check any figure here against the NEC edition your jurisdiction has adopted.

A 5 HP single-phase motor at 230 V reads 28 A. The same horsepower three-phase at 230 V reads 15.2 A.

Where the table prints no row, the page gives no figure: single-phase rows stop at 10 HP, and three-phase rows stop at 150 HP at 208 V and 230 V and at 300 HP at 460 V and 575 V. Our motor FLA guide covers how FLA affects breaker selection, wire sizing, and overload protection in detail.

Motor branch circuit diagram showing FLA measurement point, breaker, and wire sizing. — FLA determines wire gauge, breaker size, and overload relay settings: all three components must be coordinated for safe motor operation.

The Table Current, the Nameplate and the Conductor

The table current is the figure conductors and short-circuit protection are sized from, rather than the motor nameplate. NEC 430.22 sizes the conductors that supply a single continuous-duty motor at a minimum of 125 percent of the motor full-load current, so a motor that reads 28 A in the table needs conductors of at least 35 A.

The nameplate full-load amps are the motor's own figure, and overload protection is set from them. The two differ: a Baldor L1430T, a 5 HP 230 V single-phase motor, prints 20.6 A on its nameplate against the table's 28 A.

If you have the nameplate efficiency and power factor, a current follows from them: horsepower times 746, divided by the voltage, the efficiency and the power factor, and for three-phase divided again by the square root of 3. That figure is a cross-check on the nameplate, not a code input.

If the motor will run from a battery-powered inverter, see our battery runtime calculator to estimate how long the bank lasts under that draw. If you are pulling a long run to a shop motor, voltage drop can set the gauge; use our wire distance calculator to check the drop before selecting your final gauge.

Worked Examples

Sizing Wire for a Workshop Table Saw

Context

You are installing a 3HP single-phase table saw in a detached workshop. The motor is rated 230V. The panel is 80 feet from the saw.

Calculation

Single-phase table, 230 V column, 3 HP row: 17 A.

Conductor minimum: 17 A x 1.25 = 21.25 A.

Interpretation

The conductors are sized from the 17 A table current, not from the nameplate. The 80-foot run adds voltage drop, which can call for a larger gauge than the current alone.

Takeaway

Before pulling wire, check the voltage drop over that 80-foot distance with our voltage drop calculator. Its nearest voltage to the 230 V rating is 240 V; set there, with copper and the 17 A table current, it prints a 2.24% drop on 12 AWG and 3.56% on 14 AWG, against the 3% it names for branch circuits.

Comparing Three-Phase Motor Options for a Pump Station

Context

A facility needs a 15HP pump motor. You are comparing 208V and 460V three-phase motors to decide which requires less expensive wiring.

Calculation

Three-phase table, 15 HP row: 46.2 A at 208 V and 21 A at 460 V.

Interpretation

The 460V motor draws less than half the current of the 208V option. That means smaller wire gauge, smaller conduit, and a smaller breaker, all of which reduce material and labor costs.

Takeaway

The wiring saving at 460V comes from the lower table current. To estimate running costs, use our electricity cost calculator.

Frequently Asked Questions

Glossary

Full Load Amps

The current a motor draws when operating at its rated horsepower and voltage under full mechanical load. FLA determines wire size, breaker rating, and overload protection settings for the motor circuit.

Power Factor

The ratio of real power (watts) to apparent power (volt-amps) in an AC circuit. Motors with low power factor draw more current than necessary to do the same work, increasing wire heating and energy waste.

Nameplate Data

The specifications stamped on a motor's identification plate by the manufacturer. Includes rated HP, voltage, FLA, efficiency, power factor, RPM, and frame size. Nameplate FLA governs overload-device sizing; branch-circuit conductors and short-circuit and ground-fault devices are sized from the table full-load current, not the nameplate (NEC 430.6).

Locked Rotor Current

The surge of current a motor draws at the instant of startup, before the rotor begins spinning. It is several times the full-load current. Determines breaker and starter sizing to prevent nuisance tripping.

Running a motor from a battery-powered inverter? Use our battery size for inverter calculator to find out how much battery capacity the motor needs.

Motor FLA is a starting point for proper electrical design, not the finish line. Starting method, ambient temperature, altitude and duty cycle all affect the final wire and protection sizing. Our HP to watts converter handles all three horsepower definitions. For critical or permitted installations, check the figures against the code edition your authority has adopted and consult a licensed electrician.

More Electrical calculators

Browse all electrical calculators: Motor FLA, wire sizing, voltage drop, load calculations, and transformer fusing based on NEC standards.

Last updated: October 25, 2026

Written and maintained by Dan Dadovic, Commercial Director at Ezoic Inc. & PhD Candidate in Information Sciences. On the energy side, Dan has hands-on experience with residential solar panel installation, DIY battery bank construction, off-grid power systems, wind power, and EV ownership/driving, all from building, maintaining, and operating his own systems.

Disclaimer: Calculator results are estimates based on theoretical formulas. Actual performance varies with temperature, battery age, load patterns, and equipment condition. For critical electrical work, consult a licensed electrician.

Methodology reviewed by Doc. dr. sc. Danijel Jerković-Štil, Assistant Professor, FERIT Osijek.