DIY Cost Tools
Energy Converter
CONVERSION CALCULATOR
Convert energy between joules, kilojoules, megajoules, food calories, watt-hours, kilowatt-hours, BTU, and foot-pounds.
Converted valueCalculating…
Conversion rateCalculating…
How it works
Each unit is represented by its energy in joules. The calculator multiplies by the source factor and divides by the destination factor.
Conversion formula
Converted energy = entered energy × joules per source unit ÷ joules per destination unit.
Worked example
12 kilowatt-hours equals 43.2 megajoules.
Important limits
- The food Calorie shown here is a kilocalorie, equal to 1,000 small calories.
- BTU values can vary slightly by convention; this tool uses the International Table BTU.
- Energy and power are different: energy is accumulated work, while power is the rate of energy use.
Frequently asked questions
How many joules are in one kWh?
One kilowatt-hour equals exactly 3.6 million joules.
Is a food Calorie a calorie?
A nutrition Calorie with a capital C is one kilocalorie, or 4,184 joules.
Review notes
Factors use SI joules, exact electrical relationships, and the International Table BTU. Last reviewed September 30, 2026.