Converter · NEC 430 · 1 HP = 0.7457 kW
HP to kW converter
Motor shaft power both ways — plus NEC Table 430.250 full-load amps, the 125% conductor rule, and the 250% breaker rule. Select any NEMA size; everything updates.
Last updated: October 2026
Converter · NEC 430 · 1 HP = 0.7457 kW
HP ↔ kW (motors)
Shaft power conversion plus NEC Table 430.250 full-load amps for wire and breaker sizing.
Quick presets
HP to kW — shaft power plus NEC amps
1 mechanical HP = 33,000 ft·lbf/min = 745.7 W = 0.7457 kW (NIST SP 811). Reverse: 1 kW = 1.341 HP. Mental shortcut: multiply HP by ¾ (100 HP ≈ 75 kW, exact 74.6). Metric PS is slightly different (0.7355 kW) — a 150 PS engine is ~148 HP.
Shaft kW is not electrical kW
The HP rating is shaft output. Electrical input is always higher: input kW = shaft kW ÷ efficiency. A 100 HP motor (74.6 kW shaft) at 93% draws 80.2 kW — sizing the feeder at 74.6 kW undersizes it by 7%. Enter your motor efficiency above for the true input.
NEC Table 430.250 — the only amps that matter for sizing
Conductors: 125% of table FLA per 430.22. Breakers: up to 250% for inverse-time per 430.52. The NEC table is intentionally conservative (covers older, less-efficient motors) — your nameplate FLA may read lower, but the table value governs the wire. Select any NEMA size and voltage above for the exact FLA, then carry it into thewire-size calculator for the conductor and the voltage-drop calculator for long runs.
FAQ
Motor conversion questions, answered
How many kW is 1 HP?
1 mechanical HP = 0.7457 kW shaft output. Reverse: 1 kW = 1.341 HP. A 100 HP motor produces 74.6 kW at the shaft but draws about 80 kW electrical at 93% efficiency.
What amps does a 10 HP motor draw?
NEC Table 430.250: 14 A at 460V 3-phase, 28 A at 230V. Conductor minimum is 125% (17.5 A → #12 Cu). Always use the NEC table — not nameplate — for sizing.
Is shaft kW the same as electrical kW?
No. HP ratings are shaft output. Electrical input = shaft kW ÷ efficiency. A 75 kW (100 HP) motor at 93% draws 80.6 kW. Sizing feeders at shaft kW undersizes them by 5–10%.
Can I use the service factor for conductor sizing?
No. NEMA service factor (typically 1.15) allows temporary overload operation, but NEC 430.22 requires conductors at 125% of full-load (100% HP) current. Size to FLA, not to service-factor amps.
Does this converter work offline?
Yes. FieldCalc is an installable PWA — after your first visit, this converter runs with zero signal. All math stays on your device.
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