Power Calculator (Physics)
Power (Watts)
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Power (kW)
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Power (Horsepower)
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Power (BTU/hr)
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How to Calculate Power
Power is the rate at which work is done or energy is transferred: P = W/t, where W is work in Joules and t is time in seconds. Power is measured in Watts (W), where 1 Watt = 1 Joule per second.
This calculator converts between common power units: Watts, kilowatts, horsepower (1 HP ≈ 745.7 W), and BTU per hour (1 W ≈ 3.412 BTU/hr). These conversions are essential for comparing engines, appliances, and heating/cooling systems.
Power determines how quickly work gets done. A 100W light bulb uses 100 Joules of energy every second. A car engine producing 200 HP can accelerate faster than one producing 100 HP with the same vehicle weight.
Frequently Asked Questions
What is the formula for power?
P = W/t (work divided by time) or equivalently P = Fv (force times velocity). Units are Watts (W).
What is a Watt?
One Watt equals one Joule per second. It measures the rate of energy transfer or conversion.
How many Watts in a horsepower?
1 mechanical horsepower ≈ 745.7 Watts. A 200 HP car engine produces about 149,140 Watts.
What is the difference between power and energy?
Power is the RATE of energy use (Watts = J/s). Energy is the total amount (Joules or kWh). A 100W bulb running 10 hours uses 1 kWh of energy.