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Horsepower Calculator

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Enter torque and RPM to find horsepower, or flip the calculation to find torque from a known horsepower and RPM.

Horsepower Calculator

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Horsepower
342.7 HP
Uses the standard mechanical horsepower constant of 5,252.

The formula

Horsepower = (Torque in lb-ft x RPM) / 5252 Torque = (Horsepower x 5252) / RPM
Example

300 lb-ft of torque at 6,000 RPM: HP = (300 x 6000) / 5252 ≈ 342.7 HP.

Step-by-step guide

  1. Choose whether you're solving for horsepower or torque.
  2. Enter the known value (torque or horsepower) and the RPM.
  3. Read the calculated result.

Why torque and horsepower always cross at 5,252 RPM

On a dyno chart, a torque curve and a horsepower curve always intersect at exactly 5,252 RPM - this isn't a coincidence, it's a direct mathematical consequence of the formula itself, since HP equals torque when RPM equals the constant. Below 5,252 RPM, torque numerically exceeds horsepower; above it, horsepower exceeds torque - not because one becomes physically "more important," just because of how the units and constant interact.

Common mistakes

Using Newton-meters directly in a formula built for lb-ft - convert N·m to lb-ft first (divide by about 1.356) or the result will be wrong by that same factor.
Assuming peak torque and peak horsepower happen at the same RPM - they almost never do, since horsepower depends on both torque and RPM together, and RPM keeps rising even as torque falls off past its peak.

Frequently asked questions

What's the practical difference between torque and horsepower?

Torque is the raw twisting force an engine produces at a given moment - it's what you feel as acceleration off the line. Horsepower is a rate: how much work that torque can do over time, which matters more for sustained high-speed performance.

Does this work for electric motors too?

Yes - the mechanical relationship between torque, RPM, and horsepower is the same regardless of what's producing the torque, whether it's a combustion engine or an electric motor.

What's the difference between horsepower and kilowatts?

Both measure power, just in different unit systems - 1 mechanical horsepower equals about 0.746 kilowatts. Multiply this calculator's HP result by 0.746 to convert to kW.

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