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MJ to J converter, megajoules to joules.

Type megajoules and read joules. To convert MJ to J, multiply by 1,000,000, which moves the decimal point six places to the right. The answer is exact, and kilojoules, kilowatt-hours and kilocalories sit under it.

3.6 MJ equals

3,600,000 J

1 megajoule = 1000000 J exactly1 joule = 0.000001 MJ exactly

Kilojoules3,600 kJ
Kilowatt-hours1 kWh
Kilocalories860.42065 kcal

↑↓ add 1Shift 10Alt 0.1Enter other boxS swapC copyL link

Common values, click one to use it

MegajoulesJoules
1 J
1,000 J
10,000 J
100,000 J
500,000 J
1,000,000 J
2,000,000 J
3,600,000 J
5,000,000 J
8,368,000 J
10,000,000 J
25,000,000 J
36,000,000 J
50,000,000 J
100,000,000 J
250,000,000 J
500,000,000 J
1,000,000,000 J
3,600,000,000 J
10,000,000,000 J

Megajoules to joules chart

  1. 0.000001 MJ1 J
  2. 0.001 MJ1,000 J
  3. 0.01 MJ10,000 J
  4. 0.1 MJ100,000 J
  5. 0.5 MJ500,000 J
  6. 1 MJ1,000,000 J
  7. 2 MJ2,000,000 J
  8. 3.6 MJ3,600,000 J
  9. 5 MJ5,000,000 J
  10. 8.368 MJ8,368,000 J
  11. 10 MJ10,000,000 J
  12. 25 MJ25,000,000 J
  13. 36 MJ36,000,000 J
  14. 50 MJ50,000,000 J
  15. 100 MJ100,000,000 J
  16. 250 MJ250,000,000 J
  17. 500 MJ500,000,000 J
  18. 1,000 MJ1,000,000,000 J
  19. 3,600 MJ3,600,000,000 J
  20. 10,000 MJ10,000,000,000 J

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Guide

How to convert MJ to J, and read the energy prefixes.

To convert MJ to J, multiply the megajoules by 1,000,000. So 1 MJ is 1,000,000 J, 3.6 MJ is 3,600,000 J and 0.054 MJ is 54,000 J. "Mega" means one million, so the sum needs no rounding. To go back from joules to megajoules, divide by 1,000,000 or move the decimal point six places to the left.

How to use the converter

  1. Type the energy in the Megajoules (MJ) box. The page opens on 3.6 MJ, which is one kilowatt-hour.
  2. Read the big result in Joules (J), then the cards for Kilojoules, Kilowatt-hours and Kilocalories.
  3. Press the swap button (or the S key) to turn joules into megajoules. 50,000 J becomes 0.05 MJ.
  4. Use Copy result, Copy link or Print chart. Click any row of Common values to load it.

The prefix ladder

Every step in the metric energy ladder is a factor of 1,000, and the SI prefixes are defined as exact powers of ten.

UnitSymbolJoulesPower of ten
jouleJ1100
kilojoulekJ1,000103
megajouleMJ1,000,000106
gigajouleGJ1,000,000,000109

Watch the capital letters. MJ with a capital M is a megajoule, a million joules. mJ with a small m is a millijoule, a thousandth of a joule. They differ by a factor of one billion. The same care applies to kW and mW.

Joules, watts and kilowatt-hours

One watt is one joule per second, so 100 W is 100 J every second. A 100 W lamp running for an hour uses 100 × 3,600 = 360,000 J, which is 0.36 MJ. One kilowatt-hour is 1,000 W for 3,600 s, so exactly 3,600,000 J or 3.6 MJ. That is why the card shows kilowatt-hours: 0.277778 kWh per megajoule. A battery rated at 15 Wh stores 54,000 J, which is 0.054 MJ.

Worked examples

  • 5 MJ. 5 × 1,000,000 = 5,000,000 J.
  • 0.25 MJ. 250,000 J, or 250 kJ.
  • 8.368 MJ. 8,368,000 J. This is 2,000 kcal when read on the thermochemical scale.
  • 36 MJ. 36,000,000 J, which is 10 kWh.
  • 1 MJ in food energy. 239.01 kcal.

Check the unit before you convert

Energy and power are different things. A megajoule is energy, an amount. A megawatt is power, a rate. If a bill or a spec sheet says MW or kW, use a power page such as kW to hp. If it says MJ, kJ or kWh, it is energy and this page is the right one. The exact figures for kilocalories come from NIST Special Publication 811, Appendix B.8 (checked 26 Oct 2026): 1 kcal is exactly 4,184 J on the thermochemical scale.

Common values

MegajoulesJoulesKilowatt-hours
0.001 MJ1,000 J0.0002778 kWh
0.1 MJ100,000 J0.02778 kWh
1 MJ1,000,000 J0.27778 kWh
3.6 MJ3,600,000 J1 kWh
10 MJ10,000,000 J2.77778 kWh
36 MJ36,000,000 J10 kWh
100 MJ100,000,000 J27.77778 kWh

For smaller food-energy units see KJ to calories and cal to kcal. The scientific calculator handles powers of ten when you need a different prefix.

Questions

Good to know.

How many joules are in a megajoule?

1,000,000 J. Mega means one million, so the factor is exact.

How do I convert MJ to J?

Multiply by 1,000,000. 2.5 MJ is 2,500,000 J. Move the decimal point six places to the right.

How do I convert J to MJ?

Divide by 1,000,000. 750,000 J is 0.75 MJ.

Is MJ the same as mJ?

No. MJ is a megajoule, 1,000,000 J. mJ is a millijoule, 0.001 J. The capital letter matters.

How many MJ are in a kWh?

1 kWh is exactly 3.6 MJ, because it is 1,000 W for 3,600 seconds.

How many kJ are in a megajoule?

1,000 kJ. A kilojoule is a thousand joules and a megajoule is a thousand kilojoules.

How many kcal is one megajoule?

239.01 kcal on the thermochemical scale, where 1 kcal is 4,184 J.