The formula for power is work divided by time, or P = w / t. Power is the rate at which work is done. The watt is the standard metric unit used to express power. A watt is equivalent to 1 joule per second.

Power is the amount of energy used to cause a displacement over time. When measuring work, the formula focuses on the amount of force that causes a displacement, not the amount of time it takes.

Horsepower is also used to describe the amount of power being put off by a machine. One unit of horsepower is equal to 750 watts.