Calories to Megajoules Converter
Convert Calories (cal) to Megajoules (MJ) instantly, or use the conversion table below to look up common values.
Calories to Megajoules conversion table
| 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 |
How to convert Calories to Megajoules
1 cal equals 4.184e-6 MJ. Use the converter above for any value, or read the table for common conversions.
MJ = cal × 0.000004184 · cal = MJ × 239005.7361376673Multiply a calories figure by 4.184e-6 to get megajoules, or divide it by 239,005.736138 to go the other way.
Worked examples
- 100 cal= 4.184e-4 MJ
- 500 cal= 0.002092 MJ
- 1,000 cal= 0.004184 MJ
What these units are
Calories (cal). 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.
Megajoules (MJ). 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.
All factors are exact definitions, so only the display is rounded.
Converting Calories to Megajoules in practice
Working in calories
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.
Reading the result in megajoules
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.
Multiplying a power figure in kilowatts by a duration in seconds produces joules, and a thousand of those make one megajoule. One kilowatt-hour is exactly 3.6 megajoules, the same energy under another name.
The frequent confusion is to treat a megawatt of capacity as a megawatt-hour of energy, and the same slip appears with megajoules when a rate is read as an amount. Time is the missing factor.
Megajoules and kilojoules differ only by a factor of one thousand, while the kilowatt-hour names the same energy at exactly 3.6 megajoules. Fuel data is tabulated in megajoules, electricity accounting uses kilowatt-hours, and mechanics works in joules.
Checking a calories to megajoules conversion
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 the units on this page.
One unit of electricity on a Tanzanian prepaid meter
1 kWh = 860,420.650096 cal = 3.6 MJ
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
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