Kilojoules to megajoules
One kilojoule is 0.001 megajoules, and this shows the working rather than just the answer. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
The factor
One kilojoule is 0.001 megajoules. That is the whole of the conversion: multiply by it, and nothing else happens.
And it is exact
Not rounded, not measured, not a convention that might be revised. The factor above is the definition, so an answer from it is as exact as the number you typed.
There is no shorter version
The factor is short enough to use as it stands, so nobody carries a rounded one and there is nothing to get wrong.
Going the other way
The reverse is not this sum backwards in your head. It is a different factor, 1,000, and dividing by one is not the same as multiplying by a rounded version of the other.
That one is short enough to write down exactly, which is why the conversion feels easier in this direction than the other.
How many of those decimals mean anything
The box above will give you ten decimal places because it can. Whether they mean anything is decided by your measurement, not by the arithmetic.
If you measured to the nearest kilojoule, your figure is already uncertain by half of one — so the answer is uncertain by about 0.0005 megajoules, and every digit past that is decoration. Quoting 0.00123456 when you measured with a tape is claiming a precision the tape never had.
Where these two sit
Kilojoules and megajoules both measure energy, which is why they can be converted at all. A conversion between families — a length into a weight — is not a conversion, it is a question with a missing quantity in it.
The unit converter pairs kilojoules with Calories (kcal) rather than with megajoules, because that is the conversion people ask for most. This page exists because a good many ask for this one instead.
Other conversions from kilojoules
calories · Calories (kcal) · joules · kilowatt hours · BTU · watt hours · electronvolts