Motor HP & Power Calculator.
Convert between motor power, torque, and RPM in any unit. Compute electrical input power and current for 1-phase and 3-phase induction motors. Sized for Indian 415V / 50Hz and IEC / NEMA standards.
RPM — typical: 750, 1000, 1440, 2880 (for 50 Hz Indian motors)
Leave blank to auto-compute, or enter to find required power
TORQUE
—
N·m
Power (kW)
—
Power (HP)
—
Torque (kgf·m)
—
Torque (lb·ft)
—
Angular speed
—
Frequency
—
P (kW) = T (N·m) × n (RPM) / 9550
P (HP) = T (lb·ft) × n (RPM) / 5252
1 HP = 0.7457 kW | 1 PS = 0.7355 kW
P (HP) = T (lb·ft) × n (RPM) / 5252
1 HP = 0.7457 kW | 1 PS = 0.7355 kW
Synchronous speed reference (50 Hz / 60 Hz)
| Poles | Sync RPM (50 Hz) | Typical full-load (50 Hz) | Sync RPM (60 Hz) | Typical full-load (60 Hz) |
|---|---|---|---|---|
| 2-pole | 3000 | 2880 | 3600 | 3450 |
| 4-pole | 1500 | 1440 | 1800 | 1750 |
| 6-pole | 1000 | 960 | 1200 | 1150 |
| 8-pole | 750 | 720 | 900 | 860 |
| 12-pole | 500 | 480 | 600 | 575 |
Motor Power Calculation
Sizing motors correctly avoids both undersizing (motor burns out) and oversizing (capital waste, poor efficiency). Calculate from electrical inputs, mechanical load, or both.
Power Formulas
3-phase: P (kW) = √3 × V × I × cos φ × η / 1000
Single-phase: P (kW) = V × I × cos φ × η / 1000
Mechanical: P (kW) = T (Nm) × N (RPM) / 9550
Worked Example: Mechanical to Electrical
Pump requires 30 Nm at 1450 RPM:
- P_shaft = 30 × 1450 / 9550 = 4.55 kW
- With 88% motor efficiency: P_input = 4.55 / 0.88 = 5.17 kW
- Select next standard size: 5.5 kW (7.5 HP) motor
Motor Sizing Considerations
- Service factor: Continuous-rated motors run at 100% nameplate. Most have SF 1.15 for short overloads.
- Starting torque: Pumps and fans have low starting torque (~20% running). Conveyors and crushers can need 200-300%.
- Inrush current: Direct-online start draws 6-8× FLC. Verify supply transformer capacity.
- VFD sizing: VFD must handle peak motor current, not just average.
Indian Industrial Voltage Standards
- 415V 3-phase: standard industrial supply
- 230V single-phase: small motors, <3 HP
- 3.3kV / 6.6kV / 11kV: large motors >100 kW often run on HT
Related Tools
For pump applications, see Pump Power Calculator. For drive systems, Speeds & Feeds and Gear Calculator.