Energy Converter - Joules, Calories, kWh, BTU & More
Convert energy values between Joules, Calories, Kilocalories, Watt-hours, Kilowatt-hours, BTU, and foot-pounds.
Converted Values
Joules (J)
3,600,000
Kilojoules (kJ)
3,600
Calories (cal)
860,420.6501
Kilocalories / Food Calories (kcal)
860.4207
Watt-hours (Wh)
1,000
British Thermal Units (BTU)
3,412.1282
Foot-pounds (ft·lb)
2,655,219.7194
How to Convert Between Energy Units
Energy is measured differently depending on context — joules in physics, calories in nutrition, kilowatt-hours on electricity bills, and BTUs for heating and cooling equipment. This converter treats the joule as a common base unit: your input is converted to joules first, then converted from joules into every other supported unit at once.
Example
1 kilowatt-hour (kWh), the unit your electricity bill is measured in, equals 3,600,000 joules, about 860,421 calories, or roughly 3,412 BTU. That single kWh is also enough energy to lift a very large mass a considerable height, illustrated here as about 2.65 million foot-pounds.
Common Use Cases
- Converting electricity usage (kWh) into other energy units for comparison.
- Converting food energy (kcal/Calories) into joules for scientific calculations.
- Converting heating/cooling capacity between BTU and kWh or joules.
FAQs
What's the difference between a calorie and a Calorie?
A lowercase "calorie" (small calorie) is the energy needed to raise 1 gram of water by 1°C. The "Calorie" used on nutrition labels is actually a kilocalorie — 1,000 small calories — which is why this converter lists Kilocalories/Food Calories (kcal) as the nutrition-label unit.
Why is a BTU not a round number of joules?
The BTU (British Thermal Unit) was originally defined as the energy to raise 1 pound of water by 1°F — an imperial-unit definition that doesn't translate to a clean round number in the metric, joule-based system, hence the 1,055.06 conversion factor.
How accurate are these conversion factors?
The factors used (for example, 1 kWh = 3,600,000 J exactly, and 1 cal = 4.184 J) are standard, internationally recognized values, so results are accurate to the number of decimal places shown.