Unit category

Energy Conversions

Convert between joules, kilowatt-hours, calories and BTU and review the units commonly used for stored energy and heat.

Convert all Energy and Power units

Live result

0.001 kJ1 J = 0.001 kJ

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Detailed guide to Energy and Power

Energy measures an amount of work or heat, distinct from power, which measures the rate energy is transferred (see the separate Power category).

This category groups practical energy conversions often needed in building systems, electricity billing and heat calculations.

Physical quantity
Energy
SI unit
Joule
Common billing unit
Kilowatt-hour
Typical use
Electrical consumption and heat content

What is energy?

Energy measures an amount of work or heat stored or transferred, not the rate at which it happens.

A kilowatt-hour is an energy unit; the related power unit (kilowatt) has its own conversion category.

Joules, kilowatt-hours, calories and BTU

The joule is the SI unit of energy. Kilowatt-hours are widely used on electricity bills, while calories and BTU are common in nutrition and heating contexts.

Energy and power units

UnitSymbolInformation
JouleJView unit guide
Kilowatt-hourkWhView unit guide

Sources

The definitions and conversion relationships on this page are aligned with standard metrology and SI reference material.

  1. BIPM: The International System of Units (SI Brochure)
  2. NIST: NIST Guide to the SI — Appendix B.8: Factors for Units Listed Alphabetically (horsepower, watt-hour dahil)
  3. NIST: Guide to the SI — Conversion Factors

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