CalcBoard / All Unit Converters / Energy

Energy Converter

Joules, calories, kilowatt-hours, and BTU — the units that food labels, electricity bills, and datasheets each insist on using.

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Energy is one quantity with a unit for every industry. Food labels use kilocalories, electricity meters use kilowatt-hours, heating and cooling equipment uses BTU, and physics uses joules and electron volts. They all measure the same thing.

The naming trap worth knowing: the “calorie” on a nutrition label is really a kilocalorie — 1000 small calories, or 4184 joules. Both are listed separately below, so a 250 kcal snack converts to 1,046 kJ, which is the figure you will see on European packaging.

Energy Converter

1 Kilocalorie = 4.184 Kilojoule
Converted in your browser. Nothing is sent anywhere.

This page’s converter uses ordinary JavaScript numbers, so long results round like any web calculator. CalcBoard’s in-app converter uses exact decimal arithmetic and works with no connection at all.

Common energy conversions

Common energy conversions for 1, 5 and 100 units
Conversion15100
Kilocalorie → Kilojoule4.18420.92418.4
Kilojoule → Kilocalorie0.239005741.195028723.900574
Kilowatt-hour → Joule360000018000000360000000
BTU → Kilojoule1.05505595.2752793105.50559
Calorie → Joule4.18420.92418.4
Watt-hour → Joule360018000360000

Every energy unit CalcBoard converts

All 8 units in this category, with the exact factor each one uses to reach the base unit (joule). These are the same constants the app computes with.

Every energy unit with its conversion factor and tier
UnitIn joulesTier
Joule1Premium
Kilojoule1000Premium
Calorie4.184Premium
Kilocalorie4184Premium
Watt-hour3600Premium
Kilowatt-hour3600000Premium
BTU1055.05585262Premium
Electron volt0.0000000000000000001602176634Premium

Convert without a browser

This page needs a connection. The CalcBoard app does the same conversions offline, with exact decimal arithmetic, and puts the converter next to a working calculator — so you can convert a measurement in one panel and immediately use it in a formula in the next, without copying anything by hand.

Free vs. Premium, honestly: the free app includes 2 panels, basic mode, 3 converter categories, and your last 10 history entries — no ads, no time limits. A one-time $2.99 purchase (no subscription) unlocks scientific and programmer modes, up to 8 panels, the shared value tray, all 10 converter categories, full history with search and CSV export, and all themes and button styles.

Frequently Asked Questions

Is a food calorie the same as a calorie?
No. A nutrition-label Calorie is a kilocalorie: 1000 calories, or 4184 joules. A 500 kcal meal is 2,092 kJ. Both units are in the list below so you can convert either one.
How many joules are in a kilowatt-hour?
Exactly 3,600,000 joules — one kilowatt sustained for 3600 seconds. It is the unit your electricity bill is measured in.
What is a BTU?
A British thermal unit, used for heating and air-conditioning capacity. One BTU is about 1055.06 joules, so a 12,000 BTU/hour air conditioner is roughly 3.5 kilowatts of cooling.

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