Energy Converter
Convert between joules, calories, kilowatt-hours, BTU, electronvolts, tonnes of TNT, and more. Enter any value and all units update in real time.
Convert energy
Quick references
Full conversion table
Enter an energy value above to see all conversions.
Food energy quick-reference
Common foods and their energy content in both kcal and kJ.
Real-world energy reference
Familiar events and objects — from a photon of light to a nuclear bomb.
kWh cost estimator
Estimate the electricity cost of any energy amount at your tariff.
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UK Ofgem price cap rate: ~24.5p/kWh (2025). Check your bill for your exact tariff.