Kilowatt-hours to megajoules (kWh to MJ)

The formula

MJ = kWh × 3.6

Where the factor comes from — each unit by its definition, then its size in SI:

• 1 kWh = 1000 × Wh = 3,600,000 J
• 1 MJ = 1000 × kJ = 1,000,000 J

Dividing the two SI sizes gives the factor: 3.6, exact — every step above is a definition, not a measurement. The reverse factor is 0.277777777778.

The SI unit of energy is the joule. Food labels use kilocalories, electricity bills kilowatt-hours, heating specs BTU and particle physics electronvolts — the same quantity in five costumes.

Worked examples

• A day's food (2000 kcal): 2.32444 kWh = 8.368 MJ — 2.32444 × 3.6 = 8.368
• A 1 kW heater run for one hour: 1 kWh = 3.6 MJ — 1 × 3.6 = 3.6
• Lifting 1 kg through 1 m at standard gravity (9.80665 J): 2.72407 × 10⁻⁶ kWh = 9.80665 × 10⁻⁶ MJ — 2.72407 × 10⁻⁶ × 3.6 = 9.80665 × 10⁻⁶
• A visible-light photon (2 eV): 8.90098 × 10⁻²⁶ kWh = 3.20435 × 10⁻²⁵ MJ — 8.90098 × 10⁻²⁶ × 3.6 = 3.20435 × 10⁻²⁵

Frequently asked questions