OTHER · ENERGY CONVERTER
Energy Converter Calculator
Convert between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, and foot-pounds using exact NIST-defined conversion factors.
3600
kJ
1 kWh = 3600 kJ
About This Calculator
Convert any energy measurement between SI, metric, and imperial units instantly — from joules and kilowatt-hours to food Calories (kcal), BTU, and foot-pounds.
How It Works
Select a source unit and a target unit, then enter your value. The converter expresses every unit relative to the joule (the SI base), multiplies by the source factor, and divides by the target factor — no approximation involved.
The Formula
result = value × factor(from) ÷ factor(to), where each factor is the unit's exact size in joules (e.g. 1 kWh = 3,600,000 J; 1 kcal = 4184 J; 1 BTU = 1055.05585262 J).
Frequently Asked Questions
- What is the difference between a calorie and a Calorie (kcal)?
- A "food Calorie" with a capital C is a kilocalorie (kcal) — 1000 small calories, or 4184 J. Nutrition labels always use kcal even when they print "calories".
- How many joules are in a kilowatt-hour?
- Exactly 3,600,000 J (3.6 MJ), because 1 watt = 1 joule per second and an hour is 3600 seconds.
- Which BTU definition does this use?
- The International Table (IT) BTU, defined as exactly 1055.05585262 J — the value used in HVAC and energy work.