Power Conversion Calculator
Our free electrical & magnetic converter handles power conversion conversions. See tables, ratios, and examples for quick reference.
Reviewed by Manoj Kumar, Mathematics Educator
Formula
Converted Value = Input x (From Factor / To Factor) | dBm = 10 x log10(P_mW)
Power conversion uses the watt as the base SI unit. Linear units convert by multiplying by the source factor and dividing by the target factor. The dBm scale is logarithmic: dBm = 10 x log10(power in milliwatts). Each 3 dB increase doubles the power, and each 10 dB increase multiplies power by 10.
Worked Examples
Example 1: Motor Power Rating
Problem:A motor is rated at 5 mechanical horsepower. Convert to watts, kilowatts, and BTU/h.
Solution:Watts = 5 x 745.7 = 3728.5 W\nKilowatts = 3728.5 / 1000 = 3.7285 kW\nBTU/h = 3728.5 x 3.41214 = 12,723 BTU/h\nThis is a typical small industrial motor rating.
Result:5 hp = 3728.5 W = 3.73 kW = 12,723 BTU/h
Example 2: Wireless Signal Power
Problem:A Wi-Fi router transmits at 20 dBm. What is this in watts and milliwatts?
Solution:P_mW = 10^(20/10) = 10^2 = 100 mW\nP_W = 100 / 1000 = 0.1 W\n20 dBm is the typical maximum allowed power for Wi-Fi in many countries.
Result:20 dBm = 100 mW = 0.1 W
Frequently Asked Questions
What is a watt and how does it relate to other power units?
A watt (W) is the SI unit of power, defined as one joule per second. It measures the rate of energy transfer or conversion. One watt equals the power produced when one ampere of current flows through one volt of potential difference (P = V x I). Common multiples include kilowatts (1 kW = 1000 W) for household appliances, megawatts for power plants, and milliwatts for electronic signals. The watt is named after Scottish inventor James Watt.
What are the most common unit conversion mistakes?
Common errors include confusing fluid ounces with weight ounces, mixing up miles and nautical miles, forgetting that UK and US gallons differ (UK is 20% larger), using the wrong temperature formula, and not accounting for the difference between troy and avoirdupois ounces.
References
Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy