Physics calculator
Power Calculator
Convert work completed over time into watts, kilowatts, and mechanical horsepower.
Time must be greater than zero. This calculates average mechanical power, not electrical power from voltage and current.
Power
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Mechanical power formula
Power measures how quickly work is performed or energy is transferred. P is power in watts, W is work in joules, and t is elapsed time in seconds. One watt equals one joule per second.
Worked examples
Transferring 1,000 J in 10 s produces 100 W. Transferring 3,600,000 J in one hour also produces 1,000 W, or 1 kW.
Scope and limitations
This calculator finds average physical or mechanical power over a time interval. Electrical power is commonly calculated from voltage and current with P = VI; use the Ohm’s Law Calculator for that relationship.
Frequently asked questions
What is the difference between watts and kilowatts?
One kilowatt equals 1,000 watts.
Which horsepower conversion is used?
The result uses mechanical horsepower, where 1 hp is approximately 745.6999 W.
Why must time be greater than zero?
Power divides energy by time, so zero time would make the calculation undefined.