Kilowatt-hours to kilocalories (food Calories) (kWh to kcal)

The formula

kcal = kWh × 860.4206501

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

• 1 kWh = 1000 × Wh = 3,600,000 J
• 1 kcal = 1000 × cal = 4,184 J

Dividing the two SI sizes gives the factor: 860.420650096 (rounded for display; the underlying ratio is fixed by the definitions). The reverse factor is 0.00116222222222.

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: 2.32444 kWh = 2,000 kcal — 2.32444 × 860.4206501 = 2,000
• A 1 kW heater run for one hour: 1 kWh = 860.421 kcal — 1 × 860.4206501 = 860.421
• Lifting 1 kg through 1 m at standard gravity (9.80665 J): 2.72407 × 10⁻⁶ kWh = 0.00234385 kcal — 2.72407 × 10⁻⁶ × 860.4206501 = 0.00234385
• A visible-light photon (2 eV): 8.90098 × 10⁻²⁶ kWh = 7.65859 × 10⁻²³ kcal — 8.90098 × 10⁻²⁶ × 860.4206501 = 7.65859 × 10⁻²³

Frequently asked questions