Watt-hours to joules (Wh to J)

The formula

J = Wh × 3,600

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

• 1 Wh = W × h = 3,600 J
• 1 J is the SI unit of energy.

Dividing the two SI sizes gives the factor: 3,600, exact — every step above is a definition, not a measurement. The reverse factor is 0.000277777777778.

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): 2,324.44 Wh = 8,368,000 J — 2,324.44 × 3,600 = 8,368,000
• A 1 kW heater run for one hour (1 kWh): 1,000 Wh = 3,600,000 J — 1,000 × 3,600 = 3,600,000
• Lifting 1 kg through 1 m at standard gravity: 0.00272407 Wh = 9.80665 J — 0.00272407 × 3,600 = 9.80665
• A visible-light photon (2 eV): 8.90098 × 10⁻²³ Wh = 3.20435 × 10⁻¹⁹ J — 8.90098 × 10⁻²³ × 3,600 = 3.20435 × 10⁻¹⁹

Frequently asked questions