Joules to Megajoules Converter
Convert Joules (J) to Megajoules (MJ) instantly, or use the conversion table below to look up common values.
Joules to Megajoules conversion table
| Joules (J) | Megajoules (MJ) |
|---|---|
| 1 | 1e-6 |
| 2 | 2e-6 |
| 3 | 3e-6 |
| 4 | 4e-6 |
| 5 | 5e-6 |
| 10 | 1e-5 |
| 25 | 2.5e-5 |
| 50 | 5e-5 |
| 100 | 1e-4 |
How to convert Joules to Megajoules
1 J equals 1e-6 MJ. Use the converter above for any value, or read the table for common conversions.
MJ = J × 0.000001 · J = MJ × 1000000Multiply a joules figure by 1e-6 to get megajoules, or divide it by 1,000,000 to go the other way.
Worked examples
- 1 J= 1e-6 MJ
- 5 J= 5e-6 MJ
- 10 J= 1e-5 MJ
- 25 J= 2.5e-5 MJ
- 100 J= 1e-4 MJ
What these units are
Joules (J). 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.
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 Joules to Megajoules in practice
Working in joules
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.
Multiples of the joule such as the kilojoule and megajoule are exact powers of one thousand, so no precision is lost. A watt is a rate rather than an amount, so it must be multiplied by time to yield joules.
The usual slip is to quote an electricity meter reading in joules when the meter counts kilowatt-hours. Both name energy, but the joule figure is 3.6 million times the kilowatt-hour figure.
The joule is the base unit, the kilojoule and megajoule are its decimal multiples, and the kilowatt-hour is the accounting unit an electricity meter counts. Joules suit physics and small quantities, while kilowatt-hours suit billing and storage capacity.
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 joules 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 = 3,600,000 J = 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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