What Is Power?
Power is the rate at which work is done or energy is transferred. In physics it is defined as the amount of work performed per unit of time. The standard unit of power is the watt (W), where one watt equals one joule of work per second. This calculator works for any system of consistent units and is universal — it applies anywhere physics does.
How to Use This Calculator
Enter the work or energy transferred in joules and the time taken in seconds, then read the resulting power in watts. The calculator also converts the result into mechanical horsepower so you can compare it against engine or motor ratings.
The Formula Explained
The power equation is $$P = \frac{W}{t}$$ where P is power in watts, W is work or energy in joules, and t is time in seconds. Doubling the work done in the same time doubles the power; doing the same work in half the time also doubles the power. Because dividing by zero is undefined, the time must be greater than zero.
Worked Example
Suppose a motor does 1,000 joules of work in 10 seconds. Then $$P = \frac{1000}{10} = 100 \text{ watts}$$ Converting to horsepower: \(\frac{100}{745.7} \approx 0.134 \text{ hp}\). So the motor outputs 100 W, a little over one-tenth of a horsepower.
FAQ
What is one watt? One watt is one joule per second — the rate of doing one joule of work each second.
How do I convert watts to horsepower? Divide watts by 745.7 for mechanical horsepower (e.g. 746 W ≈ 1 hp).
Can I use this for electrical power? Yes — electrical energy in joules over time in seconds gives the average power in watts, the same as \(P = VI\) averaged over time.
