Automotive Tools

Horsepower Calculator

Calculate horsepower from torque and RPM, or convert watts to HP. Get instant results in multiple units.

Calculation Mode

Torque

lb-ft

RPM

Horsepower

285.61 HP

Kilowatts212.98 kW

Metric Horsepower289.57 PS

Input300.00 lb-ft @ 5,000.00 rpm

FormulaHP = (Torque × RPM) ÷ 5252

What is the Horsepower Calculator?

Horsepower (HP) is a unit of power measuring how fast work is done. One horsepower equals 745.7 watts. Horsepower can be calculated from torque and RPM using the formula: HP = (Torque in lb-ft × RPM) ÷ 5252. It can also be converted directly from watts. The calculator also shows results in kilowatts (kW) and metric horsepower (PS).

How it works

Choose your input method: torque and RPM, or watts. For torque mode, enter torque in lb-ft and engine RPM. For watts mode, enter power in watts. The calculator instantly computes horsepower and displays results in HP, kW, and PS.

From torque: HP = (Torque × RPM) ÷ 5252. From watts: HP = Watts ÷ 745.7.

The torque-to-horsepower formula divides the product of torque and RPM by 5252, a constant that accounts for unit conversion. The 5252 value comes from converting RPM to radians per second and normalizing the units. For watts conversion, divide by 745.7 because one horsepower equals exactly 745.7 watts. The calculator also converts to kilowatts (1 kW = 1000 W) and metric PS (1 HP ≈ 1.01387 PS).

Examples

Input	Result	Notes
Torque 300 lb-ft at 5000 RPM	285.70 HP	Common peak horsepower spec for a turbocharged four-cylinder. Calculation: (300 × 5000) ÷ 5252 = 285.70 HP ≈ 213 kW ≈ 289.95 PS.
Torque 500 lb-ft at 3500 RPM	331.53 HP	Typical for a naturally-aspirated V8. Calculation: (500 × 3500) ÷ 5252 = 331.53 HP ≈ 247.3 kW ≈ 336.59 PS.
200,000 watts	268.15 HP	Electric motor or engine power in watts. Calculation: 200000 ÷ 745.7 = 268.15 HP ≈ 200 kW ≈ 271.72 PS.

How to use the Horsepower Calculator

Choose your calculation mode: Torque & RPM or Watts

If using torque mode: enter the torque value in lb-ft and the RPM

If using watts mode: enter the power in watts

The calculator displays horsepower in HP, kW, and metric PS immediately

Review the stats section to see the input values, formula used, and conversions

Benefits

Instant conversion — no manual formula lookups or spreadsheets required

Dual-mode input — calculate from torque and RPM, or directly from watts

Multiple units — results displayed in HP, kilowatts (kW), and metric horsepower (PS)

Perfect for automotive comparisons — easily compare engine specs across different power measurements

Supports decimals — enter precise values like 285.5 HP or 5750 RPM

Tips & common mistakes

Common mistakes

Confusing torque and horsepower — torque is twisting force (lb-ft), horsepower is the rate of work (HP); they measure different things

Entering horsepower directly instead of torque — the calculator needs torque in lb-ft and RPM, not horsepower input

Forgetting RPM when calculating from torque — both torque AND RPM are required; one alone is not enough

Using the wrong constant — 5252 is the correct divisor for lb-ft to HP, not 5250 or other values

Tips

Peak horsepower occurs at a specific RPM; the same torque at lower RPM yields less horsepower

Metric horsepower (PS) is slightly higher than SAE horsepower (HP) by about 1.4%; most cars use the SAE measurement

Engine torque curves are often published at peak power RPM; use that RPM with the peak torque for best accuracy

When comparing engines, note the RPM at which max power and torque occur—a lower-RPM peak may mean better everyday driving

Frequently asked questions

What is the difference between torque and horsepower?

Torque is the twisting force an engine produces, measured in lb-ft or Nm. Horsepower is how fast the engine does work. An engine can have high torque at low RPM but low horsepower if the RPM is low. Horsepower = (Torque × RPM) ÷ 5252.

What does 5252 mean in the formula?

5252 is a conversion constant that accounts for the units: it converts lb-ft per minute to horsepower. It comes from the mathematical relationship between rotational force and work rate. Always use 5252 for this formula.

Can I convert lb-ft torque to Nm (Newton-meters)?

Yes. One lb-ft equals approximately 1.35582 Nm. Multiply your torque in lb-ft by 1.35582 to get Nm. The calculator displays results in HP, kW, and PS regardless of torque units.

What is metric horsepower (PS)?

PS (Pferdestärke) is the metric horsepower unit used in Europe and elsewhere. One HP ≈ 1.01387 PS. The difference is about 1.4%, so a 200 HP engine is about 202.8 PS.

Is the calculator accurate for real engines?

Yes, if you use accurate torque and RPM values from your engine's dyno test or spec sheet. The formula is mathematically precise. However, real-world engine output varies by load, temperature, and fuel quality.

Can I use this for electric motors or turbines?

Yes. If you know the torque in lb-ft and rotational speed in RPM, the formula works. Alternatively, enter the motor's rated power in watts for instant HP conversion.