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Horsepower
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The complete HP calculator hub — engine horsepower, torque conversions, quarter-mile, pump & motor HP, and 50+ more tools. All math runs in your browser, instantly.

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Horsepower Calculator
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HORSEPOWER
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The Fundamentals

How to Calculate Horsepower

Three formulas cover almost every real-world HP calculation. Bookmark this page — it's the only reference you need.

Method 1
HP = Torque × RPM
÷ 5252
Torque in lb-ft · Engine speed in RPM
Method 2
HP = W × (MPH ÷ 234)³
W = weight in lbs · MPH = trap speed
Method 3
HP = Watts ÷ 745.7
Or: HP = kW × 1.341
All Formulas & Methods →
57 Free Tools

All Horsepower Calculators

The only HP calculator hub that covers the entire power universe — automotive, racing, industrial, and beyond.

Horsepower Calculators
15 tools
Engine HP, wheel HP, flywheel, BHP, boost, drivetrain loss, altitude correction, and more.
Torque & RPM Boost HP HP/Ton Altitude Loss
Power & Torque Conversions
18 tools
HP↔kW, HP↔torque, HP↔amps, Nm↔lb-ft, watts, BTU, knots, MPH — every unit covered.
HP to kW HP to Amps Nm to lb-ft HP to MPH
Motor, Pump & Industrial HP
5 tools
Electric motor HP, pump HP, hydraulic HP, AC tonnage & motor HP-to-amps chart.
Motor HP Pump HP Hydraulic HP AC Tonnage
Drag Racing & Performance
9 tools
Power-to-weight ratio, quarter-mile ET & MPH, HP from ET, 0–60, trap speed, gear ratio & tire size.
Power/Weight Quarter Mile HP from ET 0–60 mph
Engine Builder Calculators
5 tools
Displacement, compression ratio, volumetric efficiency, CFM-to-HP & injector sizing.
Displacement Comp Ratio CFM to HP Injector Size
Quick Tools & Utilities
5 tools
HP unit converter, car HP comparison, formula reference sheet, motor HP lookup & induction HP.
Unit Converter HP Compare Formula Sheet

📚 Learn Hub — 10 In-Depth Guides

What is horsepower? HP vs torque, the 5252 rule, WHP vs crank HP, boosted engines & more.

Browse Guides →

Horsepower Formulas

Engine HP (Torque)

HP = Torque × RPM ÷ 5252

HP from Trap Speed

HP = Weight × (MPH ÷ 234)³

Quarter-Mile ET

ET = 6.290 × (W ÷ HP)⅓

HP ↔ kW

kW = HP × 0.7457

Pump HP

HP = GPM × PSI ÷ 1714

Motor HP (3-Phase)

HP = √3 × V × I × Eff × PF ÷ 746

Wheel HP (Drivetrain)

WHP = HP × (1 – loss%)

Power-to-Weight

PWR = HP ÷ Weight (lbs)

HP from Watts

HP = Watts ÷ 745.7
Full Formula Reference Sheet →

Frequently Asked Questions

Use the formula: HP = (Torque × RPM) ÷ 5252. For example, 400 lb-ft at 5252 RPM = exactly 400 HP. The constant 5,252 is derived from unit conversions: 1 HP = 33,000 ft-lb/min, and when you divide 33,000 by 2π you get 5,252. This means HP and torque curves always cross at 5,252 RPM.

1 mechanical horsepower = 745.7 watts = 0.7457 kW = 550 ft-lb/sec = 33,000 ft-lb/min. Metric horsepower (PS) = 735.5 watts. Electric horsepower = 746 watts exactly. Use our HP to kW calculator for any conversion.

Use the trap-speed method: HP = Weight × (Trap MPH ÷ 234)³. Or use Hale's ET formula: HP = Weight × (Speed ÷ 234)³. A 3,200 lb car with a 112 MPH trap speed has approximately 400 HP. Try our Trap Speed HP Calculator or the HP from ET Calculator.

Flywheel / Crank HP is measured at the engine output shaft — the figure manufacturers advertise. BHP (Brake Horsepower) is essentially the same, measured by a brake applied to the engine. WHP (Wheel Horsepower) is measured at the wheels on a chassis dyno, after drivetrain losses (typically 10–22%). Read our full guide on WHP vs Crank HP.

The torque×RPM÷5252 formula is mathematically exact. Trap-speed and ET formulas are accurate to ±3–5% for stock vehicles on good track prep. Boost/turbo estimates vary more (±15%) because VE and intercooler efficiency are unknown. Engine-build estimates are rough targets. For precise numbers, use a professional dynamometer. All results on this site are estimates — see our disclaimer.