Convert joules to calories and other energy units instantly. Supports calorie, kilocalorie, joule, kilojoule, BTU, watt-hour, and kilowatt-hour — all displayed simultaneously.
Enter any energy value below, select its unit, and see the equivalent in all supported energy units instantly.
Quick reference table for common energy values across all supported units.
| Joules (J) | Calories (cal) | Kilocalories (kcal) | Kilojoules (kJ) | BTU | Watt-hours (Wh) | Kilowatt-hours (kWh) |
|---|---|---|---|---|---|---|
| 1 J | 0.2390 cal | 0.0002390 kcal | 0.001 kJ | 0.0009478 BTU | 0.0002778 Wh | 2.778 × 10⁻⁷ kWh |
| 4.184 J | 1 cal | 0.001 kcal | 0.004184 kJ | 0.003966 BTU | 0.001162 Wh | 1.162 × 10⁻⁶ kWh |
| 1,000 J | 239.0 cal | 0.2390 kcal | 1 kJ | 0.9478 BTU | 0.2778 Wh | 0.0002778 kWh |
| 4,184 J | 1,000 cal | 1 kcal | 4.184 kJ | 3.966 BTU | 1.162 Wh | 0.001162 kWh |
| 10,000 J | 2,390 cal | 2.390 kcal | 10 kJ | 9.478 BTU | 2.778 Wh | 0.002778 kWh |
| 100,000 J | 23,900 cal | 23.90 kcal | 100 kJ | 94.78 BTU | 27.78 Wh | 0.02778 kWh |
| 1,000,000 J | 239,006 cal | 239.0 kcal | 1,000 kJ | 947.8 BTU | 277.8 Wh | 0.2778 kWh |
| 3,600,000 J | 860,421 cal | 860.4 kcal | 3,600 kJ | 3,412 BTU | 1,000 Wh | 1 kWh |
Follow these simple steps to convert between any energy units:
💡 Tip: The highlighted result shows the unit most commonly associated with your input. For example, if you enter joules, the calorie equivalent is highlighted; if you enter calories, the joule equivalent stands out.
Energy is measured in many different units depending on the context — from physics labs to kitchen nutrition labels. Here is a brief overview of each unit supported by this converter.
The SI base unit of energy. One joule equals the energy transferred when a force of one newton displaces an object by one meter. Used universally in science and engineering.
Originally defined as the energy needed to raise 1 gram of water by 1 °C. Commonly used in chemistry and physics. 1 cal = 4.184 J exactly.
Equal to 1,000 calories. This is the "Calorie" shown on food labels (capital C). 1 kcal = 4,184 J. Used in nutrition and food science worldwide.
Equal to 1,000 joules. Commonly used on nutrition labels outside the US, especially in Australia, New Zealand, and parts of Europe. 1 kJ = 0.239 kcal.
British Thermal Unit. The energy needed to raise 1 pound of water by 1 °F. Widely used in HVAC, heating, and cooling systems, especially in the United States. 1 BTU ≈ 1,055.06 J.
Units of electrical energy. 1 Wh = 3,600 J (one watt of power for one hour). 1 kWh = 3,600,000 J. Used for electricity billing and battery capacity ratings.
To convert joules to calories, divide the number of joules by 4.184. For example, 4,184 J ÷ 4.184 = 1,000 calories (which is also 1 kilocalorie). This converter does the math instantly for you — simply enter joules in the input and select "Joule" as the unit.
One kilocalorie (kcal) equals 1,000 calories (cal). In food labeling, when you see "Calories" with a capital C, it actually refers to kilocalories. So 1 food Calorie = 1 kcal = 4,184 J. This is a common source of confusion — the converter handles both units so you can see the difference clearly.
One BTU (British Thermal Unit) equals approximately 1,055.06 joules. BTU is commonly used in heating, ventilation, and air conditioning (HVAC) to measure heating and cooling capacity. For reference, 1 kWh ≈ 3,412 BTU.
Divide the number of joules by 3,600 to get watt-hours. This is because 1 watt-hour equals 3,600 joules (1 watt of power sustained for 3,600 seconds). For example, 3,600 J = 1 Wh, and 3,600,000 J = 1 kWh — roughly the energy used by a typical microwave running for one hour.
A joule (J) is the SI standard unit of energy. In everyday terms: one joule is roughly the energy required to lift a small apple (about 100 grams) one meter upward against gravity. A 60-watt light bulb consumes 60 joules of energy every second. Understanding joules helps connect different energy measurements across physics, nutrition, and engineering.
Different fields and regions developed their own convenient units over time. Calories are traditional in chemistry and nutrition (especially in the US), BTU was standardized for the heating/cooling industry, watt-hours are natural for electrical measurements, and joules are the scientific SI standard. This converter lets you move seamlessly between all of them without manual calculation.