Energy conversion
How to convert energy
Energy can be expressed in mechanical, electrical, thermal, or food-related units. Convert through joules and verify which calorie definition is intended.
Open the energy converterUse joules as a common reference
target value = source value × source joules per unit ÷ target joules per unit
One kilojoule is 1,000 joules. One watt-hour is 3,600 joules because a watt is one joule per second and an hour contains 3,600 seconds.
Convert kilowatt-hours
One kilowatt-hour equals 3.6 megajoules. Therefore, 2.5 kWh × 3.6 = 9 MJ. To convert megajoules back to kWh, divide by 3.6.
A kilowatt-hour is energy, not power. It records one kilowatt sustained for one hour or another power-time combination with the same total.
Calories and food Calories
A thermochemical calorie is 4.184 J. A food Calorie, written with a capital C in everyday nutrition, is a kilocalorie and equals 4,184 J. Thus 500 kcal equals 2,092 kJ.
Thermal and mechanical units
BTU definitions vary slightly, so identify the convention when high precision matters. Foot-pounds are also energy units and should not be confused with pound-feet used for torque. Keep the source definition with your result.
Convert with ToolPixels
The free Energy Converter converts the supported units in your browser. Enter a value, choose the source and target units, select the needed precision, and review the displayed formula before using the result.