Energy Converter
Convert an energy between joules, calories, kilocalories, watt-hours, kilowatt-hours, BTU and foot pound-force.
Result
Worked example
1 kWh = 3,600,000 J = 3.6 MJ exactly. 1 kcal = 4,184 J, so 2,000 kcal = 8.368 MJ. 1 BTU = 1,055.05585262 J, and 1 kWh ≈ 860.4206501 kcal.
How it works
Every unit converts through the joule using exact defined factors: 1 Wh = 3,600 J and 1 kWh = 3.6 MJ. The calorie (cal) here is the thermochemical calorie, exactly 4.184 J, and the kilocalorie (kcal) is exactly 4,184 J. The “Calorie” printed on food labels is a kilocalorie, not a calorie, so it is listed as the kilocalorie rather than as a separate unit. The BTU is the International Table BTU, 1,055.05585262 J, and a foot pound-force is 0.3048 m × 4.4482216152605 N. Electronvolts and other specialist units are not included.
Signed values are accepted: a negative energy can represent a change or balance, such as a net loss. Energy is an amount and power is a rate: 1 kW running for one hour is 1 kWh. For a rate, use the Power Converter.
A result written as a plain number is exact. A result starting with “≈” has been rounded to 10 significant figures, because its exact decimal never ends or is too long to read comfortably. When an exact value is long, its full digits are shown underneath. The calculation itself is never rounded: only the display is.
What this result means
The converted value uses exact, defined conversion factors. A plain number is exact; a result starting with “≈” is rounded to 10 significant figures.
Common mistakes
- Mixing up the calorie (cal) with the kilocalorie (kcal): one kilocalorie is 1,000 calories.
Assumptions and limitations
- The calorie is the thermochemical calorie (4.184 J); the food-label “Calorie” is the kilocalorie.
- Electronvolts, therms and other specialist units are not included.
Sources and review
- NIST Special Publication 811, Appendix B.8: conversion factors
- ISO 80000-5 (International Table BTU)