Enter your energy in joules and time in seconds into the Joules to Watts Calculator to find your power output in watts — plus quick conversions to kilowatts and horsepower so you've got every unit covered.
Power
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Power (Kilowatts)
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Power (Horsepower)
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The formula is P(W) = E(J) / t(s), where P is power in watts, E is energy in joules, and t is time in seconds. Power equals energy divided by time.
A joule (J) is the SI unit of energy. One joule equals the energy required to move a 1-kilogram object 1 meter using a constant force of 1 newton.
A watt (W) is the SI unit of power, measuring the rate of energy transfer. One watt equals one joule per second, indicating how fast energy is being used or produced.
Divide the energy in joules by the time in seconds. For example, 250 joules over 40 seconds equals 6.25 watts (250 ÷ 40 = 6.25).
Yes, you can calculate energy in joules by multiplying power in watts by time in seconds: E(J) = P(W) × t(s). This gives you the total energy consumed or produced.
Energy is the capacity to do work (measured in joules), while power is the rate at which energy is transferred or consumed (measured in watts). Power tells you how fast energy is being used.
Using the formula P = E/t, 1000 joules divided by 10 seconds equals 100 watts. This means the power output is 100 watts during that 10-second period.
Power (watts) is energy per unit time, so you need both energy and time to calculate it. Without time, you only have total energy but no indication of how quickly it's being used.