Power Calculator
Enter the work done and the time it took, and get the power in watts — the single number that tells you how fast energy is being transferred.
Work and time in, power out
Enter the work in joules and the time in seconds and the calculator returns the power (work ÷ time) in watts, plus the equivalent in horsepower.
Mind the units
Keep work in joules and time in seconds — one watt is exactly one joule per second, so consistent units give a result straight in watts.
What is a power calculator?
Work over time, one clear number
A power calculator turns two measurements — how much work was done (the energy transferred) and how long it took — into a single number: the power, the rate at which energy is moving. Power is what separates a sprint from a stroll covering the same distance, and it is the figure that rates engines, sizes appliances, and measures athletic output. Because one watt is defined as one joule per second, the formula is as direct as physics gets.
Enter the work in joules and the time in seconds to get the power in watts instantly.
One short formula: divide the work by the time.
P = work ÷ timeThe capital letter P is the standard symbol for power. Because power is work divided by time, the units follow automatically: joules ÷ seconds gives joules per second, which is the watt (W). The same 100 W can also be read as roughly 0.134 horsepower, since one mechanical horsepower is 745.699872 W.
Suppose you do 1000 joules of work in 10 seconds.
Note the work and time
1000 joules of energy transferred, over 10 seconds — keep work in joules and time in seconds so the result lands in watts.
Divide work by time
1000 ÷ 10 = 100 — the energy delivered each second.
Read the power
100 W, which is about 0.134 hp — the steady output of a bright incandescent light bulb.
The single power figure is really a statement about speed, not size. Power is the rate of doing work, so the same job done faster always needs more power: carry a load upstairs in five seconds instead of ten and you double the power even though the energy spent is identical. That is why two engines that ultimately do the same total work can be rated very differently — the one that finishes sooner is the more powerful. The watt makes this concrete: a 100 W light bulb consumes 100 joules of energy every single second it stays on, and a 2000 W kettle pours 2000 joules per second into the water. Converting to horsepower (1 hp ≈ 745.7 W) is handy for engines and motors, where 100 W is a modest 0.134 hp and a family car might deliver well over a hundred horsepower. Read your result as "joules per second" and its meaning is immediate.
The formula is exact, but a couple of practical points are worth keeping in mind.
Average power, consistent units, and the right quantity
This calculator gives the average power over the time you enter: if the rate of work varies, peak power can be much higher than the average. The result is only meaningful when work is in joules and time in seconds — mixing units (kilojoules, minutes) skews the answer. And power is the rate of energy transfer, not the energy itself: to recover the total energy, multiply the power back by the time in seconds.