What is brake horsepower (BHP)?

Brake horsepower is the power output measured directly at the engine crankshaft using a brake or dynamometer. It does not account for drivetrain losses. BHP = (Torque in lb-ft × RPM) / 5252. It is the most common power rating in British automotive specs.

What is the difference between BHP, HP, and PS?

BHP (brake horsepower) and mechanical HP are equivalent at approximately 1:1 (1 HP = 1 BHP in the mechanical system). PS (Pferdestärke, metric horsepower) is slightly smaller: 1 BHP ≈ 1.01387 PS. kW is the SI unit: 1 BHP ≈ 0.7457 kW. European manufacturers often quote PS; British manufacturers use BHP; North American ones use HP.

Why is the constant 5252 used in the formula?

One horsepower is defined as 33,000 ft-lb of work per minute. Combining that with the rotational formula Power = Torque × angular velocity (2π × RPM / 60) and simplifying gives the constant 33,000 / (2π) ≈ 5252. This is why HP and torque curves always intersect at exactly 5252 RPM.

How do I convert lb-ft to Nm?

Multiply lb-ft by 1.35582 to get Nm. For example, 300 lb-ft = 406.7 Nm. This tool converts automatically when you switch the unit toggle.

Is BHP the same as wheel horsepower (WHP)?

No. BHP is measured at the engine. WHP (wheel horsepower) is measured at the driven wheels and is lower due to drivetrain losses — typically 10–20% less in rear-wheel-drive cars, slightly more in AWD. This tool calculates BHP (crankshaft power), not WHP.

Can I use this for diesel engines?

Yes. The formula BHP = Torque × RPM / 5252 applies to any internal combustion or electric motor regardless of fuel type. Diesel engines typically produce peak torque at lower RPM than petrol engines but the physics are identical.

Brake Horsepower Calculator

Name: Brake Horsepower Calculator
Availability: InStock
Author: Nham Vu

Enter torque (lb-ft or Nm) and RPM to instantly calculate BHP, kW, and PS — the three most common power units used in automotive specs.

Standard formula: BHP = Torque (lb-ft) × RPM / 5252

Torque unit:

Torque (lb-ft)

RPM

Formula Reference

Imperial (lb-ft)

BHP = Torque × RPM / 5252

Metric (Nm)

kW = Torque × RPM / 9549

Conversions: 1 lb-ft = 1.35582 Nm • 1 BHP = 0.7457 kW • 1 BHP ≈ 1.01387 PS

Enter values on the left to see the result

Summary

Enter torque (lb-ft or Nm) and RPM to instantly calculate BHP, kW, and PS — the three most common power units used in automotive specs.

How it works

Select whether you want to calculate BHP from torque, or torque from BHP.
Choose your torque unit: lb-ft (pound-feet) for imperial, or Nm (Newton-meters) for metric.
Enter the torque value and the engine RPM in the input fields.
BHP, kW, and PS are calculated instantly using the standard power formula.
Switch to Reverse mode to find the torque needed to hit a target BHP at a specific RPM.
Use the formula reference card to understand the math behind the conversion.

Use cases

Verify manufacturer BHP specs against published torque curves.
Convert dyno-measured torque at peak RPM to a BHP figure.
Compare BHP vs PS specs when reading European car reviews.
Check engine tuning results — did the cam and tune deliver the expected BHP?
Calculate the torque required to hit a target BHP at a chosen RPM.
Cross-check BHP and kW figures for international spec sheets.
Estimate power output for custom engine builds before dynoing.
Understand why HP and torque curves always cross at 5252 RPM.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu