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How It Works
Power measures how fast energy is transferred or work is done. This calculator supports three formulas: P = W/t (work over time), P = F·v (force times velocity), and P = V·I (voltage times current). The SI unit is the watt (W), equal to one joule per second.
Example Problem
An engine exerts 200 N of force on a car moving at 15 m/s. What power does it deliver?
- P = F · v = 200 × 15 = 3,000 W (3 kW)
In electrical terms, a 120 V outlet supplying 10 A delivers 120 × 10 = 1,200 W.
Frequently Asked Questions
What is the difference between power and energy?
Energy is the total amount of work done or heat transferred (measured in joules). Power is the rate at which that energy is used (joules per second, or watts). A 100 W bulb uses 100 J every second.
How do you convert watts to horsepower?
One mechanical horsepower equals about 745.7 W. Divide watts by 745.7 to get HP. For example, 3,000 W ÷ 745.7 ≈ 4.02 HP.
What is a kilowatt-hour?
A kilowatt-hour (kWh) is a unit of energy, not power. It equals the energy consumed by a 1 kW device running for one hour: 1 kWh = 3.6 MJ.
Related Calculators
- Work Calculator — calculate work from force and displacement.
- Kinetic Energy Calculator — find the energy of a moving object.
- Force Equation Calculator — determine the force component of P = Fv.
- Horsepower Calculator — convert between horsepower and watts for engines and motors.
- Ohm's Law Calculator — compute electrical power from voltage and current.
- Power Unit Converter — convert between watts, kilowatts, and horsepower.
Reference: Lindeburg, Michael R. 1992. Engineer In Training Reference Manual. Professional Publication, Inc. 8th Edition.