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Sources and Accuracy
Energy conversions use joule as the reference unit, including electrical, thermal, nutrition, and mechanical energy units.
Displayed results are rounded for readability. The calculator keeps enough precision for everyday use and switches to scientific notation for very large or very small values. Last reviewed: 2026-05-21.
About These Units
kilojoule [kJ]
Definition
The kilojoule is an energy unit equal to 1000 joules.
History
Kilojoules are a metric multiple of joules and became common where joules are too small.
Current use
Kilojoules are used for food energy labels, thermodynamics, exercise energy, and engineering calculations.
kilowatt-hour [kWh]
Definition
The kilowatt-hour is an energy unit equal to the energy used by one kilowatt of power for one hour.
History
Kilowatt-hours became common through electric utility metering and billing.
Current use
Kilowatt-hours are used for electricity bills, batteries, appliances, solar systems, and energy planning.