Megajoules to kilowatt-hours (MJ to kWh) converter

What is a megajoules to kilowatt-hours converter?

A megajoules to kilowatt-hours converter is an online tool that turns an amount of energy expressed in megajoules (MJ) into its equivalent in kilowatt-hours (kWh), and back again. Both units measure the same physical quantity, energy, but they belong to different worlds: the megajoule is the scientific, SI-derived unit built on the joule, while the kilowatt-hour is the commercial unit you see on electricity bills and energy meters. Being able to move between them is handy whenever a figure quoted in one unit needs to be understood in the other.

How it works

The joule (J) is the base SI unit of energy. A megajoule is one million joules, and a kilowatt-hour is the energy delivered by one kilowatt of power running for one full hour. Since one kilowatt is 1,000 watts and one hour is 3,600 seconds, a kilowatt-hour equals 1,000 × 3,600 = 3,600,000 joules, or 3.6 MJ.

The converter first expresses your input in joules, then divides by the size of the target unit. To go from megajoules to kilowatt-hours, it multiplies by one million (to reach joules) and divides by 3,600,000, which simplifies to dividing by 3.6. Going the other way, it multiplies kilowatt-hours by 3.6 to get megajoules. Because the relationship is an exact constant, the conversion is precise and never depends on the substance or context being measured.

Formula

To convert megajoules to kilowatt-hours, divide by 3.6:

$\text{kWh} = \frac{\text{MJ}}{3.6}$

To convert kilowatt-hours back to megajoules, multiply by 3.6:

$\text{MJ} = \text{kWh} \times 3.6$

Conversion table

The table below lists common megajoule values and their kilowatt-hour equivalents, rounded to a sensible number of decimals.

Examples

Example 1: 1 megajoule to kilowatt-hours

Convert 1 MJ to kilowatt-hours by dividing by 3.6:

$\frac{1}{3.6} = 0.277778 \text{ kWh}$

So 1 megajoule equals about 0.277778 kilowatt-hours.

Example 2: 18 megajoules to kilowatt-hours

A common round case is 18 MJ, which falls on an exact figure:

$\frac{18}{3.6} = 5 \text{ kWh}$

So 18 megajoules is exactly 5 kilowatt-hours.

Example 3: 1 kilowatt-hour to megajoules

To find the megajoule value of a single kilowatt-hour, multiply by 3.6:

$1 \times 3.6 = 3.6 \text{ MJ}$

A single kilowatt-hour, the unit your electricity meter counts, holds 3.6 megajoules of energy.

Example 4: 10 kilowatt-hours to megajoules

For a larger figure, take 10 kWh:

$10 \times 3.6 = 36 \text{ MJ}$

So 10 kilowatt-hours equals 36 megajoules.

Notes

• The relationship between the two units is exact: 1 kWh = 3.6 MJ, with no rounding involved in the constant itself.
• Kilowatt-hours describe energy, not power. Power (in kilowatts) tells you the rate, while a kilowatt-hour is the amount accumulated over time.
• Electricity bills, battery capacities, and solar generation are usually quoted in kilowatt-hours, whereas scientific and engineering work often prefers megajoules.
• Any rounding you see in the table or examples comes from display formatting, not from the conversion factor.

Frequently asked questions

How many kilowatt-hours are in a megajoule?

One megajoule equals about 0.277778 kilowatt-hours, found by dividing 1 by 3.6.

How many megajoules are in a kilowatt-hour?

One kilowatt-hour equals exactly 3.6 megajoules, because 1 kWh is 3,600,000 joules and 1 MJ is 1,000,000 joules.

Why is the conversion factor 3.6?

A kilowatt-hour is 1,000 watts sustained for 3,600 seconds, which is 3,600,000 joules, or 3.6 MJ. That makes 3.6 the exact bridge between the two units.

Is a megajoule bigger than a kilowatt-hour?

No. A kilowatt-hour (3.6 MJ) is larger than a single megajoule. You need 3.6 megajoules to make one kilowatt-hour.

How do I convert 18 megajoules to kilowatt-hours by hand?

Divide 18 by 3.6, which gives 5 kilowatt-hours. The same divide-by-3.6 rule works for any megajoule value.

Are these units interchangeable with joules?

Yes. Both are simply multiples of the joule: 1 MJ is 1,000,000 J and 1 kWh is 3,600,000 J, so every value can also be expressed in joules.