How to Calculate Engine Power in Kilowatts

Vehicles' power ratings can be given in horsepower or watts.

Most automobiles are rated in terms of horsepower, although there are a variety of units of measure that can be used. Contrary to popular belief, one horsepower is defined as 33,000 lb.-ft. per minute, not "the amount of work a horse can do." This figure was created by the inventor of the steam engine, John Watt -- for whom the famous unit of power measurement is named -- after he calculated how much work horses did as they turned a mill.

Things You'll Need

• Pencil
• Paper
• Calculator
• Stopwatch
• Quarter mile track

Instructions

1. Find your vehicle's horsepower. It should be listed in your owner's manual, or you can contact your car's manufacturer to get the rating.

2. Multiply the horsepower rating by 745.699. This is the number of watts in one horsepower. Dividing that product by 1,000 will give your engine's power in kilowatts.

3. Measure your car's weight on a scale.

4. Drive your car to a quarter mile track, and time how long it takes to cover the quarter mile with a stopwatch.

5. Divide your car's quarter mile time by 5.825 and cube the quotient. Divide your car's weight by this to give its measurement in horsepower, and finally multiply that by 745.699 to give your vehicle's measured power in watts.

Tips & Warnings

• Always obey the speed limit and traffic laws when measuring quarter mile time.

References

• DSM: Simple Horsepower Calculator
• Airlink Transformers: How do I Convert Horse Power to Watts?