Calories Converter
Convert Calories (cal) to any other energy unit. The table below gives the exact figure for each unit, and every conversion is worked from the same engine as the converter.
What calories convert to
One cal in every other energy unit.
| Unit | 1 cal | Reverse |
|---|---|---|
| Joules | 4.184 J | 0.239006 cal |
| Kilojoules | 0.004184 kJ | 239.005736 cal |
| Megajoules | 4.184e-6 MJ | 239,005.736138 cal |
| Watt-hours | 0.001162 Wh | 860.42065 cal |
| Kilowatt-hours | 1.1622e-6 kWh | 860,420.650096 cal |
| Kilocalories | 0.001 kcal | 1,000 cal |
| BTU | 0.003966 BTU | 252.164401 cal |
Multiply a calories figure by the figure in the second column to get the unit in the first, or multiply by the third column to go the other way.
Calories conversion reference
Calories to Joules
One calories is 4.184 joules, and one joules is 0.239006 calories.
The joule is the SI unit of energy: the work done by one newton over one meter. It is used for small energy amounts in physics and engineering.
- 1 cal= 4.184 J
- 5 cal= 20.92 J
- 10 cal= 41.84 J
Energy in the International System of Units is measured in joules, where one joule is the work done by a force of one newton moving an object one metre. The symbol is J.
Physics and engineering use the joule for mechanical work, heat, radiation and electrical energy, and small appliance labels sometimes state a surge or pulse rating in joules.
Calories to Kilojoules
One calories is 0.004184 kilojoules, and one kilojoules is 239.005736 calories.
A kilojoule is 1,000 joules. It is used for food energy in most countries outside the United States, and for small industrial figures.
- 1 cal= 0.004184 kJ
- 5 cal= 0.02092 kJ
- 10 cal= 0.04184 kJ
One kilojoule is exactly 1,000 joules, and the symbol is kJ. It is the joule multiple that food packaging commonly prints, with energy shown in kilojoules beside kilocalories, and chemistry uses it for reaction energies.
Nutrition panels, exercise machines and dietary advice report energy in kilojoules wherever the metric system is used. Materials and fuel data, such as energy content per kilogram, are tabulated in kilojoules as well.
Calories to Megajoules
One calories is 4.184e-6 megajoules, and one megajoules is 239,005.736138 calories.
A megajoule is 1,000 kilojoules, or about 0.278 kilowatt-hours. It is used for the energy content of fuels: a litre of diesel holds roughly 36 megajoules.
- 100 cal= 4.184e-4 MJ
- 500 cal= 0.002092 MJ
- 1,000 cal= 0.004184 MJ
One megajoule is 1,000 kilojoules, which is one million joules. Fuels, industrial processes and large energy figures are quoted in megajoules when a count in joules would be unwieldy.
Fuel energy content, blast energy, industrial process heat and large-scale storage are described in megajoules. Engineering calculations for combustion and materials testing also use the unit.
Calories to Watt-hours
One calories is 0.001162 watt-hours, and one watt-hours is 860.42065 calories.
A watt-hour is the energy of one watt sustained for one hour — 3,600 joules. It is used for battery and power-bank capacity; a phone battery is typically 10 to 20 watt-hours.
- 1 cal= 0.001162 Wh
- 5 cal= 0.005811 Wh
- 10 cal= 0.011622 Wh
Calories to Kilowatt-hours
One calories is 1.1622e-6 kilowatt-hours, and one kilowatt-hours is 860,420.650096 calories.
A kilowatt-hour is 1,000 watt-hours, or 3.6 megajoules. It is the unit on electricity bills, and the 'unit' shown on a prepaid meter.
- 100 cal= 1.1622e-4 kWh
- 500 cal= 5.8111e-4 kWh
- 1,000 cal= 0.001162 kWh
The kilowatt-hour is the energy of one kilowatt sustained for one hour, and it is exactly 3.6 megajoules. Its symbol is kWh, and it equals 1,000 watt-hours.
Electricity bills, prepaid meter units, solar generation totals and battery or power-bank capacity are all measured in kilowatt-hours. Appliance consumption over time is compared in the same unit.
Calories to Kilocalories
One calories is 0.001 kilocalories, and one kilocalories is 1,000 calories.
A kilocalorie is 1,000 calories, or 4,184 joules. It is the 'calorie' on food labels, so a 2,000-calorie diet means 2,000 kilocalories.
- 1 cal= 0.001 kcal
- 5 cal= 0.005 kcal
- 10 cal= 0.01 kcal
Exactly 1,000 thermochemical calories, or 4,184 joules, make one kilocalorie. A food label that prints calorie, often with a capital letter, means this unit rather than the small calorie of physics.
Food energy on packaging, diet plans, restaurant menus and sports nutrition is stated in kilocalories. Physiology and nutrition research also reports energy expenditure in the same unit.
Calories to BTU
One calories is 0.003966 btu, and one btu is 252.164401 calories.
A BTU (British thermal unit) is 1,055.05585262 joules — the energy needed to heat one pound of water by one degree Fahrenheit. It is used for heating and cooling capacity.
- 1 cal= 0.003966 BTU
- 5 cal= 0.019828 BTU
- 10 cal= 0.039657 BTU
What calories are used for
A calorie here is the small calorie of 4.184 joules — the energy needed to raise one gram of water by one degree Celsius. Food labels use the kilocalorie, which is 1,000 of these.
One thermochemical calorie is exactly 4.184 joules, a definition fixed by convention rather than by a water experiment. The food calorie on a nutrition label is a kilocalorie of 4,184 joules.
The small calorie appears in chemistry, physics and heat-capacity problems, where a substance's specific heat is expressed per gram per degree. Nutrition labels use the much larger food calorie instead.
Calories convert to joules by the exact factor 4.184, and kilocalories by 4,184, so no precision is lost in either direction. One kilocalorie is about 4.184 kilojoules, the same amount under another name.
Reading a nutrition label's calorie value as small calories understates the energy by a factor of one thousand. The figure printed there is always the kilocalorie, however it is capitalised or labelled.
The calorie shares its dimension with the kilocalorie, the joule and the kilojoule, and mixing them is the risk. A food label's figure is a kilocalorie, while mechanics and heat problems work in joules and kilojoules.
All factors are exact definitions, so only the display is rounded.
Energy units are defined against the joule, so every conversion in this dimension is a single exact multiplication by a published number rather than a chain of steps that could accumulate error.
The pair that needs care is the kilowatt-hour, because it looks like a power unit and is not. It is a watt sustained for an hour, which is why an electricity meter counts in kilowatt-hours while a generator is rated in kilowatts: one is an amount, the other is a rate, and only a duration links them.
To check an energy conversion, express both sides in joules or both in kilowatt-hours before comparing. The commonest mistake is treating a food calorie as a calorie when the label means a kilocalorie, which understates the figure a thousandfold.
Tanzania reference points
Real quantities, converted into calories.
One unit of electricity on a Tanzanian prepaid meter
1 kWh = 860,420.650096 cal
The average domestic rate was about 229.59 TZS per kWh as of December 2025, including taxes and supply. That is an average across domestic customers, not the marginal rate on a bill.
Source: GlobalPetrolPrices — Tanzania electricity prices (compiled from EWURA/TANESCO tariffs) · verified 2026-09-14
Calories conversion tables
Calories to Joules
| Calories (cal) | Joules (J) |
|---|---|
| 1 | 4.184 |
| 2 | 8.368 |
| 3 | 12.552 |
| 4 | 16.736 |
| 5 | 20.92 |
| 10 | 41.84 |
| 25 | 104.6 |
| 50 | 209.2 |
| 100 | 418.4 |
Calories to Kilojoules
| Calories (cal) | Kilojoules (kJ) |
|---|---|
| 1 | 0.004184 |
| 2 | 0.008368 |
| 3 | 0.012552 |
| 4 | 0.016736 |
| 5 | 0.02092 |
| 10 | 0.04184 |
| 25 | 0.1046 |
| 50 | 0.2092 |
| 100 | 0.4184 |
Calories to Megajoules
| Calories (cal) | Megajoules (MJ) |
|---|---|
| 1 | 4.184e-6 |
| 2 | 8.368e-6 |
| 3 | 1.2552e-5 |
| 4 | 1.6736e-5 |
| 5 | 2.092e-5 |
| 10 | 4.184e-5 |
| 25 | 1.046e-4 |
| 50 | 2.092e-4 |
| 100 | 4.184e-4 |