Kwh to Mj
Convert any value from kilowatt-hour to megajoule with full precision. Use the converter above for instant results, or read on for the exact formula, worked examples, common uses, and answers to frequently asked questions.
About the Kilowatt-Hour to Megajoule conversion
Energy appears in many different units depending on the field. Physics uses joules, nutrition uses calories and kilocalories, electricity uses kilowatt-hours, heating and air-conditioning use BTU (British Thermal Units), and particle physics uses electronvolts. Converting between them correctly is essential in science, engineering, and everyday life.
This page focuses specifically on converting kilowatt-hour to megajoule. Use the converter above for instant results, or read on for what each unit is, the exact formula, a worked example, and answers to common questions.
Understanding kilowatt-hour and megajoule
What is a kilowatt-hour?
The kilowatt-hour is the energy used by a one-kilowatt appliance running for one hour, equal to exactly 3.6 million joules. It is the unit electric utilities use to bill households, so it is the most common energy unit on a power bill.
What is a megajoule?
The megajoule equals one million joules. It is convenient for describing larger amounts of energy such as the output of engines, food energy in scientific work, and heating loads.
How a kilowatt-hour compares to a megajoule
The kilowatt-hour is the larger of the two units: one kilowatt-hour is about 3.6 megajoule. Because the megajoule is smaller, the same length or quantity works out to a larger number when you measure it with that unit. Knowing which unit is larger is a quick way to sanity-check a conversion: if the numbers move in the wrong direction, the two units have probably been swapped.
Conversion formula
The exact mathematical relationship between kilowatt-hour and megajoule is:
1 kilowatt-hour = 3.6 megajoule
So to convert a value V from kilowatt-hour to megajoule, use:
Vmegajoule = Vkilowatt-hour × 3.6
To go in the opposite direction:
Vkilowatt-hour = Vmegajoule × 0.27777778
These factors come from the international definitions published by NIST, BIPM, and ISO 80000 and are exact within their respective standard systems. The converter applies them with full floating-point precision.
Worked example
Using the formula above, here are some common values converted from Kilowatt-Hour to Megajoule:
| Kilowatt-Hour | Megajoule |
|---|---|
| 1 | 3.6 |
| 5 | 18 |
| 10 | 36 |
| 25 | 90 |
| 50 | 180 |
| 100 | 360 |
Sources and accuracy
The joule is the SI unit of energy, defined as the work done by a force of one newton over one meter (BIPM, NIST). One calorie equals exactly 4.184 joules by international definition. One BTU equals exactly 1055.05585262 joules. One electronvolt equals exactly 1.602176634×10⁻¹⁹ joules (since the 2019 SI redefinition).
Conversion factors are cross-checked against the NIST SP 811 guide, the BIPM SI brochure, and ISO 80000, plus published historical references for older unit systems. For mission-critical work such as medical dosing, legal-for-trade measurement, aerospace, or large-scale engineering, always verify independently with the original source.
Practical tips
When reading food labels, "calories" almost always means kilocalories (1 kcal = 1,000 cal = 4,184 J). When sizing air conditioners, one "ton" of cooling equals 12,000 BTU per hour.
Frequently asked questions
How many megajoule are in one kilowatt-hour?
One kilowatt-hour equals 3.6 megajoule. To convert, multiply your kilowatt-hour value by 3.6.
Which is bigger, a kilowatt-hour or a megajoule?
The kilowatt-hour is bigger. One kilowatt-hour equals about 3.6 megajoule.
How accurate is this kilowatt-hour to megajoule converter?
It uses the official international conversion factors from NIST and BIPM with full double-precision floating-point accuracy. For everyday use the result is precise to many more decimal places than any practical measurement requires.
Can I convert megajoule back to kilowatt-hour as well?
Yes. Use the swap button above to reverse the From and To fields, or change either dropdown to any unit in the energy category. The calculation runs entirely in your browser, so it also works offline once the page has loaded.