Engine Horsepower Calculator

What Engine Horsepower is for

Engine Horsepower Calculator is the page to open when you need engine horsepower from measurements you already have. It belongs with the other automotive calculators because that is the work this arithmetic supports. Type the entries first. The result stays hidden until you press Calculate, so a half-finished form never flashes a number you might mistake for the answer.

How to fill in this calculator

1. Time. Enter the value this part of the job needs. The unit list on this field includes s, ms.
2. Weight. Enter the value this part of the job needs. The unit list on this field includes lbs, tons, kg.

The formula in plain language

Horsepower and torque are tied together by rpm. Torque in pound-feet equals horsepower times 5252, divided by rpm. The quarter-mile estimate uses vehicle weight and the elapsed time: horsepower is about the weight divided by (time divided by 5.825) cubed.

A worked example

300 horsepower at 5,000 rpm is 315 pound-feet. A 3,400 pound car that runs the quarter mile in 13.0 seconds is showing roughly 305 horsepower at the tire.

Displacement, compression, airflow, and the torque curve describe one engine. This engine horsepower result should be read with carburetor size and engine torque.

Mistakes that move the answer

• The 5252 constant only works with pound-feet and horsepower, not newton-meters.
• A quarter-mile time includes traction. Spinning the tires makes the car look weaker than the engine is.

How to check the result

After Calculate shows the engine horsepower result, redo the last operation with a pencil using the rounded figures on the screen. Matching that check means the inputs were read correctly. If you edit a label or a sentence in this HTML file, reload the page. The form and this article both live in the file, so the edit is what visitors will read.