Energy Conversions

Energy conversions connect physics, nutrition, electrical power, and thermodynamics. Joules are the SI unit, but dietary energy uses calories (kcal), electricity bills use kilowatt-hours, and HVAC equipment uses BTUs. Converting accurately between these units is essential for comparing energy sources, interpreting international nutrition labels, sizing solar systems, and calculating heating and cooling loads.

  • ✓Converting calories (kcal) to kilojoules for international nutrition labels
  • ✓Converting kWh to joules for physics, electrical, and solar power calculations
  • ✓Converting BTU to watts for HVAC system sizing and energy efficiency ratings
  • ✓Converting food Calories to joules for exercise science and metabolic research

Most Popular Energy Conversions

Calories → KilojoulesKilojoules → CalorieskWh → JoulesJoules → kWhBTU → Jouleskcal → Joules

All Energy Converters

Convert from Joules (J)

Joules → KilojoulesJoules → CaloriesJoules → KilocaloriesJoules → Watt-HoursJoules → Kilowatt-HoursJoules → Electron VoltsJoules → BTUJoules → Foot-Pounds

Convert from Kilojoules (kJ)

Kilojoules → JoulesKilojoules → CaloriesKilojoules → KilocaloriesKilojoules → Watt-HoursKilojoules → Kilowatt-HoursKilojoules → Electron VoltsKilojoules → BTUKilojoules → Foot-Pounds

Convert from Calories (cal)

Calories → JoulesCalories → KilojoulesCalories → KilocaloriesCalories → Watt-HoursCalories → Kilowatt-HoursCalories → Electron VoltsCalories → BTUCalories → Foot-Pounds

Convert from Kilocalories (kcal)

Kilocalories → JoulesKilocalories → KilojoulesKilocalories → CaloriesKilocalories → Watt-HoursKilocalories → Kilowatt-HoursKilocalories → Electron VoltsKilocalories → BTUKilocalories → Foot-Pounds

Convert from Watt-Hours (Wh)

Watt-Hours → JoulesWatt-Hours → KilojoulesWatt-Hours → CaloriesWatt-Hours → KilocaloriesWatt-Hours → Kilowatt-HoursWatt-Hours → Electron VoltsWatt-Hours → BTUWatt-Hours → Foot-Pounds

Convert from Kilowatt-Hours (kWh)

Kilowatt-Hours → JoulesKilowatt-Hours → KilojoulesKilowatt-Hours → CaloriesKilowatt-Hours → KilocaloriesKilowatt-Hours → Watt-HoursKilowatt-Hours → Electron VoltsKilowatt-Hours → BTUKilowatt-Hours → Foot-Pounds

Convert from Electron Volts (eV)

Electron Volts → JoulesElectron Volts → KilojoulesElectron Volts → CaloriesElectron Volts → KilocaloriesElectron Volts → Watt-HoursElectron Volts → Kilowatt-HoursElectron Volts → BTUElectron Volts → Foot-Pounds

Convert from BTU (BTU)

BTU → JoulesBTU → KilojoulesBTU → CaloriesBTU → KilocaloriesBTU → Watt-HoursBTU → Kilowatt-HoursBTU → Electron VoltsBTU → Foot-Pounds

Convert from Foot-Pounds (ft·lbf)

Foot-Pounds → JoulesFoot-Pounds → KilojoulesFoot-Pounds → CaloriesFoot-Pounds → KilocaloriesFoot-Pounds → Watt-HoursFoot-Pounds → Kilowatt-HoursFoot-Pounds → Electron VoltsFoot-Pounds → BTU

Frequently Asked Questions — Energy

How many joules are in a calorie?
1 small calorie (cal) equals 4.184 joules. The dietary Calorie shown on food labels (written with a capital C) is actually a kilocalorie (kcal), which equals 4,184 joules. So a 200 Calorie snack contains 836,800 joules of energy.
How many joules are in a kilowatt-hour?
1 kilowatt-hour (kWh) equals 3,600,000 joules (3.6 MJ). A kWh is the energy used by a 1,000-watt appliance running for one hour. This is the unit on electricity bills — the average US household uses about 900 kWh per month.
What is a BTU and when is it used?
A BTU (British Thermal Unit) equals 1,055 joules — the energy needed to raise 1 pound of water by 1°F. It is the standard US unit for air conditioner cooling capacity (e.g., '12,000 BTU window AC'), furnace heating output, and gas appliance ratings.

Related Conversion Categories

Power Conversions

Convert between units of power for electrical, mechanical, and heating applications.

Temperature Conversions

Convert between Celsius, Fahrenheit, Kelvin, and Rankine temperature scales.

Weight Conversions

Convert between units of weight and mass from milligrams to metric tons.

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