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Horsepower Calculator | Compute Horsepower From Torque and RPM

Estimate horsepower from torque and RPM, or from quarter-mile trap speed and vehicle weight, with the formulas shown. Compare cars, plan modifications and understand the power-to-weight ratio.

Last updated: June 2026 · Free · No sign-up required

Results

Enter values above and click Calculate to see your result instantly.

Quick reference

Horsepower from torque at RPM:

Torque (lb-ft)3000 rpm5000 rpm
200114 hp190 hp
300171 hp286 hp
400228 hp381 hp

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Interpretation guide

Horsepower facts:

ConceptDetail
1 hp550 ft-lb/s or ~746 watts
HP = TQ at 5252 rpmPower and torque curves cross there
Crank vs wheel HPDrivetrain loses ~10–20%
Trap-speed estimateFrom weight and 1/4-mile speed

lightbulb Worked example

Let's say you are using the Horsepower Calculator. Enter torque in foot-pounds and engine RPM, and this horsepower calculator estimates mechanical horsepower using the standard torque formula, then converts the result to kilowatts and watts. It Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula HP = Torque(lb-ft) x RPM / 5252; trap estimate: HP = weight x (mph / 234)^3 and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: HP = Torque(lb-ft) x RPM / 5252; trap estimate: HP = weight x (mph / 234)^3

The Horsepower Calculator is built on a well-established calculation method. It uses the formula HP = Torque(lb-ft) x RPM / 5252; trap estimate: HP = weight x (mph / 234)^3 to turn your inputs into a reliable result. Enter torque in foot-pounds and engine RPM, and this horsepower calculator estimates mechanical horsepower using the standard torque formula, then converts the result to kilowatts and watts. It explains the difference The steps are shown on the page so you can follow the reasoning from input to output.

Horsepower is the rate of doing work. The calculator derives it from rotational output using HP = torque x RPM / 5252, the constant that makes the two curves cross at 5252 rpm. It can also estimate engine power from vehicle weight and quarter-mile trap speed using Hale's formula. Remember that crank horsepower is higher than wheel horsepower because the drivetrain absorbs roughly 10–20% on the way to the tires.

Authoritative source: timeanddate.com

Frequently asked questions

How do I calculate horsepower from torque?
Enter the required values into the input fields and press the calculate button. The tool applies the formula HP = Torque(lb-ft) x RPM / 5252; trap estimate: HP = weight x (mph / 234)^3 and returns the result with a short explanation of each step, so you can check the working yourself.
Why do horsepower and torque cross at 5252 rpm?
The Horsepower Calculator is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. Enter torque in foot-pounds and engine RPM, and this horsepower calculator estimates mechanical horsepower using the standard torque formula, then converts the result to kilowatts and watts. It explains the difference between mechanical, metric, and There is no limit on usage, and it works on any device.
What's the difference between crank and wheel horsepower?
Crank (brake) horsepower is the engine's output measured at the flywheel before drivetrain losses; wheel horsepower is what actually reaches the tires through the transmission, driveshaft, and axles. Typical drivetrain losses are 10–15% for rear-wheel drive and 15–20% for front- or all-wheel drive. Dyno numbers are usually wheel horsepower, while manufacturers quote crank figures.
How is horsepower estimated from a quarter mile?
Empirical formulas relate trap speed and vehicle weight to horsepower, such as HP = weight × (trap speed ÷ 234)³, since a faster trap speed at the same weight requires proportionally more power. These estimates are accurate to roughly ±5% for conventional cars. Enter your quarter-mile trap speed and weight and the calculator applies the formula.
How many watts is one horsepower?
One mechanical horsepower equals exactly 745.7 watts (0.7457 kW), by definition. One metric horsepower (PS) equals 735.5 watts — slightly less. In electrical contexts, 1 hp is commonly approximated as 746 watts for sizing motors. The calculator converts between horsepower units and kilowatts so specs from different countries compare cleanly.
What does the Horsepower Calculator do?
Enter torque in foot-pounds and engine RPM, and this horsepower calculator estimates mechanical horsepower using the standard torque formula, then converts the result to kilowatts and watts. It explains the difference between mechanical, metric, and. The calculator takes your inputs, applies the standard calculation, and returns a clear result so you can make an informed decision without doing the math by hand.
What formula does the Horsepower Calculator use?
It applies the standard torque formula HP = Torque(lb-ft) × RPM ÷ 5,252 for the dyno-based route, and the empirical trap-speed estimate HP = weight × (mph ÷ 234)³ from a quarter-mile run. Enter the torque and RPM, or the weight and trap speed, and the tool returns the estimated horsepower with the working shown.
Is the Horsepower Calculator free and private?
Yes — the Horsepower Calculator. There is no sign-up, no paywall, no trial, and no limit on how many calculations you can run. CalcaTools covers its costs with non-intrusive display advertising, so the calculator itself never asks for payment or restricts any feature.
How accurate is the Horsepower Calculator?
The Horsepower Calculator applies the standard formula: HP = Torque(lb-ft) x RPM / 5252; trap estimate: HP = weight x (mph / 234)^3. It is tested against published worked examples before launch and uses native double-precision arithmetic, so results are accurate to typical precision for the values you enter — with no intermediate rounding that could distort the answer.

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