Motor full load current (FLA) calculator
Work out the full-load current a three-phase motor draws from its nameplate power, line voltage, efficiency and power factor — the figure used to size the starter, overload relay and cable.
Three-phase full-load current
Formula: I (A) = (kW × 1000) / (√3 × V × η × PF) — kVA-basis current ignores efficiency and power factor, while apparent power is kVA = kW / PF. NEC 430.250 tables are published for standard motors at fixed voltages, so always cross-check against the nameplate for the actual motor.
Quick FLA reference
| kW | FLA (A) | Line kVA (A) |
|---|---|---|
| 0.75 | 1.4151 | 1.0825 |
| 1.5 | 2.8301 | 2.1651 |
| 2.2 | 4.1509 | 3.1754 |
| 4 | 7.5471 | 5.7735 |
| 5.5 | 10.3772 | 7.9386 |
| 7.5 | 14.1507 | 10.8253 |
| 11 | 20.7544 | 15.8771 |
| 15 | 28.3015 | 21.6506 |
| 18.5 | 34.9052 | 26.7024 |
| 22 | 41.5088 | 31.7543 |
| 30 | 56.603 | 43.3013 |
| 37 | 69.8103 | 53.4049 |
| 45 | 84.9045 | 64.9519 |
| 55 | 103.7721 | 79.3857 |
| 75 | 141.5074 | 108.2532 |
| 90 | 169.8089 | 129.9038 |
| 110 | 207.5442 | 158.7713 |
Common three-phase motor ratings at 400 V, using the same efficiency and power factor entered above. Starting current is typically 5–8× FLA.
Common NEC 430.250 values (460 V)
| Horsepower | Full-load amps (A) |
|---|---|
| 1 HP | 2.1 |
| 5 HP | 7.6 |
| 10 HP | 14 |
| 20 HP | 27 |
| 30 HP | 40 |
| 50 HP | 65 |
| 75 HP | 96 |
| 100 HP | 124 |
| 150 HP | 180 |
| 200 HP | 240 |
Standard 3-phase induction motor full-load currents at 460 V from NEC 430.250. For other voltages these values scale roughly inversely with voltage, but always use the nameplate or the applicable code table for sizing.
The full-load current is what the starter, overload relay and cable must be rated for — motor protection breakers and thermal relays are typically selected at or above the nameplate current, while VFDs are often oversized one frame. AO Ctrl stocks the switching, protection and drive gear for three-phase motors:
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Frequently asked questions
What is full load current (FLA)?
FLA is the current a motor draws at its rated power and voltage. It is the basis for sizing the contactor, overload relay, cables and the motor circuit breaker. This calculator derives it as I = P×1000/(√3 × V × η × PF) for a three-phase motor.
How is motor FLA calculated for three-phase?
FLA = (kW × 1000) / (√3 × V × η × PF), where η is efficiency and PF power factor (both from the nameplate). The NEC 430.250 table gives typical values at 460 V — for other voltages scale by 460/V.
What if the motor nameplate shows HP instead of kW?
Convert HP to kW with 1 HP = 0.7457 kW (or use the kW-to-HP tool), then compute FLA with the formula above. A 1.15 service factor motor can draw up to 115% of FLA continuously — size protection for that.
AO Ctrl provides this tool for reference only.