Energy Converter

How to convert energy units

Every energy unit is related to one base unit (Joule, J) by an exact factor. To convert, multiply by the factor of the unit you start from and divide by the factor of the unit you want.

value in new unit = value × (factor of old unit ÷ factor of new unit)

For example, 1 kWh = 3 600 000 J and 1 MJ = 1 000 000 J, so 1 kWh = 3.6 MJ.

Quick reference table

How many of the units in the column headings make up one of the unit in each row.

One…	= eV	= J	= kJ	= MJ	= Wh	= kWh
1 eV	1	1.60218 × 10⁻¹⁹	1.60218 × 10⁻²²	1.60218 × 10⁻²⁵	4.45049 × 10⁻²³	4.45049 × 10⁻²⁶
1 J	6.24151 × 10¹⁸	1	0.001	1 × 10⁻⁶	0.0002777778	2.77778 × 10⁻⁷
1 kJ	6.24151 × 10²¹	1 000	1	0.001	0.2777778	0.0002777778
1 MJ	6.24151 × 10²⁴	1 000 000	1 000	1	277.7778	0.2777778
1 Wh	2.24694 × 10²²	3 600	3.6	0.0036	1	0.001
1 kWh	2.24694 × 10²⁵	3 600 000	3 600	3.6	1 000	1
1 cal	2.61145 × 10¹⁹	4.184	0.004184	4.184 × 10⁻⁶	0.001162222	1.16222 × 10⁻⁶
1 kcal	2.61145 × 10²²	4 184	4.184	0.004184	1.162222	0.001162222
1 BTU	6.58514 × 10²¹	1 055.056	1.055056	0.001055056	0.2930711	0.0002930711
1 ft·lbf	8.46235 × 10¹⁸	1.355818	0.001355818	1.35582 × 10⁻⁶	0.0003766161	3.76616 × 10⁻⁷

Common values: kWh to MJ

Kilowatt-hour (kWh)	Megajoule (MJ)
1 kWh	3.6 MJ
2 kWh	7.2 MJ
5 kWh	18 MJ
10 kWh	36 MJ
20 kWh	72 MJ
50 kWh	180 MJ
100 kWh	360 MJ
200 kWh	720 MJ
500 kWh	1 800 MJ
1 000 kWh	3 600 MJ

Worked examples

The units explained

Unit	Symbol	Exact factor	Where it is used
Electronvolt	eV	1 eV = 1.60218 × 10⁻¹⁹ J	Atomic and semiconductor physics
Joule	J	1 J = 1 J	SI unit
Kilojoule	kJ	1 kJ = 1 000 J	Chemistry, food
Megajoule	MJ	1 MJ = 1 000 000 J	Fuel, large energies
Watt-hour	Wh	1 Wh = 3 600 J	Batteries
Kilowatt-hour	kWh	1 kWh = 3 600 000 J	Electricity bills
Calorie (thermochemical)	cal	1 cal = 4.184 J	Chemistry, lab
Kilocalorie	kcal	1 kcal = 4 184 J	Food energy
British thermal unit	BTU	1 BTU = 1 055.056 J	US heating and fuel
Foot-pound force	ft·lbf	1 ft·lbf = 1.355818 J	US mechanical work

Key facts

• 1 kWh = 3.6 MJ. Energy = power × time.
• 1 BTU is about 1.055 kJ. 1 kcal = 4.184 kJ.

Related converters, guides and tools

• Other converters: Pressure converter, Density converter, Temperature converter, Angles converter, Flow Rate converter, Time converter, Stress converter, Strain converter, Velocity converter, Volume converter, Length converter, Mass converter, Force converter, Torque converter, Power converter.
• Guides: Embedded Systems.
• Unit Conversions: every converter on one tabbed page that remembers the tabs you use.
• My Dashboard (members): put this converter on your own workspace as a widget beside the others.

FAQ

How many Megajoule units are in one Kilowatt-hour?

1 kWh = 3.6 MJ.

How do I convert kWh to MJ?

Multiply by 3.6 (the factor 3 600 000 ÷ 1 000 000). To go back, divide by 3.6 or multiply by 0.2777778.

What is the electronvolt (eV) used for?

Atomic and semiconductor physics.

What is the joule (J) used for?

SI unit.

Are the conversion factors exact?

Where a unit is defined exactly (the inch is 25.4 mm, the pound is 0.45359237 kg, standard gravity is 9.80665 m/s²) the factor is exact; others are given to ten or more digits. Results are shown to seven significant digits.

References

• NIST Special Publication 811, Guide for the Use of the International System of Units (SI), and NIST Handbook 44, Appendix C (general tables of units of measurement).
• BIPM, The International System of Units (SI Brochure), 9th edition; ISO 80000 (quantities and units).

Last reviewed: November 2026.