Motor FLA Calculator
Look up motor full-load amps straight from the NEC tables. Pick phase, horsepower, and voltage to get the table FLA and the 125% value used to size branch-circuit conductors for a single continuous-duty motor.
Motor
Full-Load Amps
FLA from NEC Table 430.250. Branch-circuit conductors are sized at 125% of FLA (NEC 430.22). Use nameplate FLA for overload sizing.
How this calculator works
This is a table lookup, not a formula — and that is the point. NEC 430.6(A)(1) requires the table full-load current values, not the motor nameplate, for sizing conductors and short-circuit protection: Table 430.248 for single-phase motors and Table 430.250 for three-phase induction motors, by horsepower and voltage. The one piece of arithmetic layered on top is the branch-circuit conductor minimum:
conductor minimum = table FLA × 1.25 (NEC 430.22, single continuous-duty motor)
The nameplate current still matters — it governs the overload protection (running protection sized to the motor actually installed), while the table value keeps the wire and breaker sizing stable when a replacement motor’s nameplate differs. Two numbers, two jobs.
Worked example
A 5 HP three-phase motor on a 230 V system:
- Table 430.250, 5 HP at 230 V: FLA = 15.2 A. (The same motor at 460 V draws exactly half — 7.6 A — a structural property of the table.)
- Branch-circuit conductor minimum: 15.2 × 1.25 = 19.0 A.
- A conductor with at least 19.0 A of ampacity after any derating — 12 AWG copper at 75°C (25 A base) covers it with margin; check the ampacity calculator if the run is hot or crowded.
These are the calculator’s default inputs (three-phase, 5 HP, 230 V) — the result panel shows both numbers.
Reference: three-phase full-load amps
Excerpt from NEC Table 430.250 — full-load current for three-phase induction motors, rendered from the same data the calculator looks up. The tool also holds the single-phase Table 430.248 values (115/230 V, 1/6 through 10 HP).
| HP | 208 V | 230 V | 460 V | 575 V |
|---|---|---|---|---|
| 1 | 4.6 A | 4.2 A | 2.1 A | 1.7 A |
| 2 | 7.5 A | 6.8 A | 3.4 A | 2.7 A |
| 3 | 10.6 A | 9.6 A | 4.8 A | 3.9 A |
| 5 | 16.7 A | 15.2 A | 7.6 A | 6.1 A |
| 7.5 | 24.2 A | 22 A | 11 A | 9 A |
| 10 | 30.8 A | 28 A | 14 A | 11 A |
| 15 | 46.2 A | 42 A | 21 A | 17 A |
| 25 | 74.8 A | 68 A | 34 A | 27 A |
| 50 | 143 A | 130 A | 65 A | 52 A |
| 100 | 273 A | 248 A | 124 A | 99 A |
Frequently asked questions
Do I size motor conductors from the nameplate FLA or the NEC table?
The table. NEC 430.6(A)(1) requires the values from Tables 430.248 (single-phase) and 430.250 (three-phase) — not the nameplate — for sizing branch-circuit conductors, disconnects, and short-circuit protection. The nameplate full-load current is used for one thing: setting the overload protection. This calculator returns the table value, which is what the conductor math starts from.
How many amps does a 5 HP motor draw?
Depends on phase and voltage. Three-phase, from NEC Table 430.250: 16.7 A at 208 V, 15.2 A at 230 V, and 7.6 A at 460 V. Single-phase, from Table 430.248: 56 A at 115 V and 28 A at 230 V. A real motor's nameplate will read somewhat different — the tables are deliberately generic so every installation of a given HP and voltage is wired the same.
What size wire do I need for a motor?
Start at 125% of the table FLA — NEC 430.22 for a single continuous-duty motor — which is the 'Conductor Min' value this calculator shows. Then pick a conductor whose ampacity at the termination temperature rating covers that number, and check voltage drop separately on long runs. Example: a 10 HP, 460 V three-phase motor is 14 A from Table 430.250, so conductors are sized for at least 17.5 A. Verify against the code edition adopted in your jurisdiction.
Why is the motor breaker allowed to be bigger than the wire ampacity?
Because the breaker on a motor circuit is only there for short-circuits and ground faults — NEC Table 430.52 lets an inverse-time breaker run as high as 250% of FLA so it rides through starting inrush without nuisance tripping. The conductors and motor are protected from overload by the separate overload relay, set from the nameplate current. It looks wrong to anyone used to 240.4, but it's how Article 430 divides the job.
My system is 480 V — do I use the 460 V column?
Yes. The NEC motor tables are listed at motor utilization voltages — 115, 200, 208, 230, 460, 575 — which correspond to nominal system voltages of 120, 208, 240, 480, and 600 V. So a motor on a 480 V system uses the 460 V column, and a 240 V system uses 230 V. The one trap: 208 V systems get their own, higher-current column — don't reuse the 230 V value (a 5 HP motor is 16.7 A at 208 V vs 15.2 A at 230 V).
Values from NEC Table 430.248 (single-phase) and Table 430.250 (three-phase induction motors); conductor minimum per NEC 430.22 (125% of table FLA, single continuous-duty motor). Per NEC 430.6(A)(1), use these table values — not the nameplate FLA — for conductor and short-circuit protective device sizing; use nameplate FLA for overload protection. Multi-motor feeders, short-time-duty motors, and synchronous machines have their own rules. Verify against the governing NEC edition.
The full tables live on the motor full-load current chart; the motor circuit data chart takes each HP the rest of the way — wire, fuse, breaker, starter, and disconnect — with the max protection percentages on the motor circuit protection chart. Pair with the Voltage Drop Calculator for long feeder runs.