Converters
Energy Converter
Convert joules, calories, kWh and BTU.
About the Energy Converter
The Energy Converter switches between joules, kilojoules, calories, kilocalories, kilowatt-hours and British thermal units, covering food labels, electricity bills and heating and cooling.
What you can do with the Energy Converter
- Converts both ways: Type in either box and the other one updates as you type.
- Every unit at once: The "In every unit" list shows your value in joules, kJ, calories, kcal, kWh and BTU. Tap one to switch to it.
- One-tap swap: The ⇅ button flips the two units, and the line under the boxes shows the rate for 1 unit.
- Food and electricity: Compare food kcal with the kWh on your electricity bill in the same list.
Food calories are kilocalories
The "Calories" on a food label are kilocalories. One kilocalorie is 4,184 joules, so a 250-Calorie snack contains about 1,046 kilojoules, which is why labels in many countries show both kcal and kJ.
Kilowatt-hours on your electricity bill
A kilowatt-hour is the energy a 1,000-watt appliance uses in one hour, equal to 3.6 million joules. In India, one "unit" on an electricity bill is one kilowatt-hour.
BTUs for heating and cooling
A British thermal unit is about 1,055 joules. Heaters and air conditioners are often rated in BTU per hour, which is a rate of energy use, a power unit, so convert those ratings with the Power Converter.
Related tools
Frequently Asked Questions
How many joules are in a calorie?
A small calorie is 4.184 joules; a food Calorie (kcal) is 4,184 joules.
How much energy is 1 kWh?
3.6 megajoules, or about 860 kcal.
Is energy the same as power?
No. Power is how fast energy is used. A 100-watt bulb uses 100 joules every second; after 10 hours it has used 1 kWh of energy.
How many kcal are in 1 kWh?
One kWh is 3.6 million joules, which is about 860.4 kcal. So one unit on an Indian electricity bill is about the same energy as 860 food Calories. Type 1 with kWh selected to see it in joules, kJ, calories, kcal and BTU.
What is the difference between a calorie and a Calorie?
A small calorie (cal) is 4.184 joules. The Calorie on food labels, with a capital C, is a kilocalorie, which is 1,000 small calories or 4.184 kJ. Indian food packs usually list energy in kcal, so pick kcal for those figures.
How do I convert kJ on a food label to kcal?
Divide kilojoules by 4.184 to get kilocalories. A label showing 1,000 kJ is about 239 kcal. Choose kJ in the first box and kcal in the second, or type the kJ value and read kcal from the "In every unit" list.
How many kWh is 2,000 kcal?
2,000 kcal is 8,368 kJ, or about 2.32 kWh. That is a typical daily food energy figure used on nutrition labels, and it is roughly what a 100-watt device uses in about 23 hours. Type 2000 with kcal selected to check.
Is one unit of electricity the same as 1 kWh?
Yes. Electricity boards in India bill in units, and one unit is one kilowatt-hour: 1,000 watts used for one hour. To estimate cost, multiply units by your tariff in rupees. This tool converts energy only and does not calculate bills.
How many BTU is 1 kWh?
One kWh is about 3,412 BTU, using 1 BTU as 1,055.06 joules. BTU appears on heaters, gas appliances and AC labels. Pick kWh and BTU, or type any value and read BTU from the "In every unit" list.
How many calories are in a joule?
One joule is about 0.239 calories, since one calorie is defined here as exactly 4.184 joules. One kilojoule is about 239 calories, or 0.239 kcal. Select joule and calorie to convert physics answers or small energy values.
Why does the answer look like 3.6e+6?
Very large or very tiny results are shown in scientific notation in the "In every unit" list. 3.6e+6 means 3.6 multiplied by 10 to the power 6, which is 3,600,000. Switch to a bigger unit, such as kJ instead of J, to get a shorter number.
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