Horsepower Calculator
Convert engine torque and RPM to horsepower, kilowatts and PS — and back
Calculation Mode
Torque (Nm)
Nm
Peak torque from engine spec sheet
Engine RPM
RPM
RPM at which peak torque occurs
Formula
Power (kW) = Torque (Nm) × RPM ÷ 9549
Power (HP) = kW × 1.341
Power (PS) = kW × 1.360
Engine Power
—
Kilowatts: —
PS (Metric Horsepower)—
Torque (Nm)—
Torque (lb-ft)—
At RPM—
What is Horsepower?
Horsepower (HP) is the unit of engine power measurement used in vehicle specifications. It was defined by James Watt to compare the output of steam engines to the power of draft horses. One horsepower equals 745.7 watts (0.7457 kW).
Modern car specs may quote power in HP (SAE — American standard), PS (metric horsepower — German/European), or kW (SI unit). These are all closely related: 1 HP ≈ 1.014 PS ≈ 0.7457 kW. Engine torque (Nm) at a specific RPM determines the power output — this calculator converts between all formats.
lightbulb Example Calculation
Scenario: A diesel engine produces 320 Nm of torque at 1,750 RPM (typical compact SUV diesel).
1kW = 320 × 1,750 ÷ 9,549 = 58.6 kW
2HP = 58.6 × 1.341 = 78.6 HP
3PS = 58.6 × 1.360 = 79.7 PS
✓ This is peak torque power — peak HP usually at higher RPM
help_outlineHow to Use the Horsepower Calculator
- Choose your mode — Torque → HP (convert torque and RPM to power) or HP → Torque (find torque from known HP and RPM).
- In Torque mode: enter the engine's peak torque in Nm and the RPM at which it occurs — find these in your car's spec sheet or owner's manual.
- In HP mode: enter the engine's peak power in HP and the RPM at which peak power occurs (different from torque peak RPM).
- Results show HP, kW, PS and torque in both Nm and lb-ft simultaneously.
- Note: peak torque and peak power occur at different RPM values — enter the RPM specific to the value you're converting from.
HP vs Torque — What's the Difference?
- Torque is the twisting force the engine produces — what you feel as pulling power and acceleration from low speeds. High torque diesel engines feel effortless at highway cruising.
- Power (HP/kW) is the rate of doing work — determines top speed and sustained performance at high RPM. Sports cars need high HP, not just high torque.
- Diesel engines produce high torque at low RPM (1,500–2,500 RPM) — great for towing and cruising
- Petrol engines produce peak power at higher RPM (5,000–7,000 RPM) — better for performance driving
- HP = Torque × RPM ÷ 5,252 (lb-ft version) or ÷ 9,549 (Nm version)
Key Terms
- HP (Horsepower)
- SAE standard used in USA and India. 1 HP = 745.7 W = 0.7457 kW. When Indians say "120 HP," they mean SAE HP.
- PS (Pferdestärke)
- German metric horsepower. 1 PS = 735.5 W = 0.9863 HP. European car specs often quote PS. 1 HP ≈ 1.014 PS — essentially the same for practical purposes.
- BHP (Brake Horsepower)
- Power measured at the crankshaft — the commonly quoted "engine power." Wheel HP is slightly lower (5–15%) due to drivetrain losses. Most quoted HP figures are BHP.
- Nm (Newton-metre)
- SI unit of torque. Most Indian and European car specs use Nm. 1 Nm = 0.7376 lb-ft. 1 lb-ft = 1.3558 Nm.
- RPM (Revolutions per Minute)
- Engine speed. Power peaks at different RPM than torque. A car spec like "320 Nm @ 1,750 RPM / 120 HP @ 3,750 RPM" has different RPMs for each peak.
quizFrequently Asked Questions
What is the difference between HP, BHP, PS and kW?
HP (horsepower) and BHP (brake horsepower) are often used interchangeably — BHP is power measured at the crankshaft via a dynamometer brake, which is the standard way most car manufacturers measure engine output. 1 HP = 0.7457 kW. PS (Pferdestärke, German for "horse strength") is the metric horsepower: 1 PS = 0.9863 HP = 0.7355 kW. For practical purposes, HP and PS are within 1.4% of each other and can be treated as equal. kW is the SI unit — most accurate and increasingly used in electric vehicle specs. A car with 100 kW has 134 HP or 136 PS.
Why does a diesel car with lower HP feel faster than a petrol car with more HP?
Because diesel engines have much higher torque available at low RPM. Everyday driving from traffic signals to 60–80 km/h uses low-to-mid RPM range — exactly where diesel torque peaks. A diesel with 160 Nm at 1,800 RPM vs a petrol with the same HP but only 120 Nm at 4,000 RPM will feel noticeably stronger in traffic. The petrol car's peak power is only accessed at high RPM (5,000–7,000), which most city drivers never reach. For sustained high-speed performance and track driving, HP matters more. For city commuting, towing, and cruising — torque at low RPM is what you actually feel.
How do I find my car's torque and RPM specs?
Your car's owner's manual (technical specifications section) lists engine power and torque. The format is usually: "Maximum Power: 88 kW (120 PS / 118 HP) at 5,200 rpm" and "Maximum Torque: 220 Nm at 1,750–2,500 rpm." You can also find these on the manufacturer's official website under the vehicle's specifications tab, or on car comparison websites like CarDekho, CarWale, or CarAndBike for Indian cars. Note that petrol and diesel variants of the same car model will have very different torque/power figures.
Can I convert lb-ft to Nm if my car spec uses imperial units?
Yes. The conversion is: 1 lb-ft = 1.35582 Nm, or equivalently 1 Nm = 0.73756 lb-ft. For quick mental math: multiply lb-ft by 1.36 to get Nm, or divide Nm by 1.36 to get lb-ft. This calculator shows torque in both Nm and lb-ft simultaneously. American and British car specifications often use lb-ft while Indian, Japanese, and European specs use Nm. For example, a V8 with "400 lb-ft of torque" = 542 Nm — roughly the same as a large diesel SUV.
Does more horsepower always mean a faster car?
Not necessarily — it depends on the power-to-weight ratio. A 100 HP car weighing 800 kg will accelerate faster than a 150 HP car weighing 2,000 kg. The ratio to look at is HP per 100 kg (or kW/tonne). Sports cars achieve this through lightweight construction rather than just more power. Aerodynamics also matters at higher speeds — drag increases with the square of velocity, so top speed gains from HP additions diminish rapidly above 160 km/h. For 0–100 km/h acceleration, torque response at launch and gear ratios matter as much as peak HP.