How to use
- Type an amount of energy in Value, such as 100 kcal.
- Pick the From and To units, or tap a popular conversion.
- Read the answer. Similar-looking units (calorie types, BTU types, therms) are labelled.
How the conversion works
Every unit has an exact size in joules (J). The converter turns your value into joules, then into the unit you want:
| Unit | Size |
|---|---|
| 1 kilocalorie (food Calorie) | 4.184 kJ |
| 1 calorie | 4.184 J |
| 1 kilowatt-hour (kWh) | 3.6 MJ ≈ 3,412 BTU |
| 1 BTU | 1,055.05585262 J |
| 1 therm (US) | ≈ 29.3 kWh ≈ 100,000 BTU |
The food Calorie on labels is a kilocalorie. Nutrition uses the thermochemical calorie of exactly 4.184 J.
Examples
- 250 kcal snack to kJ: 250 × 4.184 = 1,046 kJ
- 2,000 kcal a day: 2,000 × 4.184 = 8,368 kJ
- 10 kWh to BTU: 10 × 3,412.14 = 34,121 BTU
Conversion charts
| Kilocalories | Kilojoules |
|---|---|
| 50 kcal | 209.2 kJ |
| 100 kcal | 418.4 kJ |
| 200 kcal | 836.8 kJ |
| 250 kcal | 1,046 kJ |
| 500 kcal | 2,092 kJ |
| 1,000 kcal | 4,184 kJ |
| 2,000 kcal | 8,368 kJ |
| kWh | Megajoules | BTU |
|---|---|---|
| 1 | 3.6 | 3,412 |
| 10 | 36 | 34,121 |
| 100 | 360 | 341,214 |
| 1,000 | 3,600 | 3,412,142 |
| Therms (US) | kWh | Megajoules |
|---|---|---|
| 1 | 29.3 | 105.5 |
| 10 | 293 | 1,054.8 |
| 50 | 1,465 | 5,274 |
| 100 | 2,930 | 10,548 |
More detail: two calories, two BTUs, two therms
- Thermochemical calorie: exactly 4.184 J. Used for food energy.
- International Table calorie: exactly 4.1868 J, about 0.07% larger. Used in some engineering tables.
- BTU: the usual International Table BTU is 1,055.06 J. The thermochemical BTU is 1,054.35 J.
- Therm: the US therm (105.4804 MJ) is the unit on US gas bills. The EC therm is 105.506 MJ.
- Food labels: EU labels work out kJ and kcal separately from each nutrient, so their ratio isn’t exactly 4.184.
Comparing power ratings in kW or hp? Use the power converter.