Horsepower Calculator
Calculate mechanical horsepower from engine torque (lb-ft) and RPM using the standard HP = torque x RPM / 5252 formula.
How It's Calculated
Formula
HP = \dfrac{\text{torque (lb-ft)} \times \text{RPM}}{5252}This calculator computes mechanical horsepower from engine torque and rotational speed (RPM), using the standard formula HP = (torque in lb-ft x RPM) / 5252. The constant 5252 comes from the definition of one horsepower (33,000 ft-lbf per minute) combined with the conversion from RPM to angular velocity; 5252 is the conventional, industry-standard rounded value used across automotive and engineering references. This calculator computes torque-and-RPM horsepower directly and is not the same as the separate Engine Horsepower calculator, which estimates horsepower from vehicle weight and quarter-mile trap speed/time.
Worked Examples
525.2 lb-ft at 1000 RPM
- HP = (525.2 x 1000) / 5252 = 100 HP.
Frequently Asked Questions
Why is the constant 5252 and not a rounder number?
It derives from the physical definition 1 horsepower = 33,000 ft-lbf/min combined with the RPM-to-radians-per-second conversion (2*pi/60). The exact value is approximately 5252.113, and 5252 is the conventional rounded constant used throughout the automotive and engineering industry.
At what RPM do torque and horsepower always cross on a dyno chart?
At 5252 RPM, torque (lb-ft) and horsepower are numerically equal — this is a direct consequence of the formula's denominator, not a coincidence.
Is this the same as the Engine Horsepower calculator?
No. This calculator computes horsepower directly from torque and RPM. The Engine Horsepower calculator instead estimates horsepower from vehicle weight and quarter-mile elapsed time/trap speed — a different method for a different situation.