What is the difference between joules and calories?

A joule is the SI unit of energy, while a calorie (or kilocalorie in nutrition) is an older unit. 1 kilocalorie equals 4,186.8 joules. Food energy is typically measured in kilocalories (often labeled as "Calories" with a capital C).

How much energy does 1 kWh represent?

1 kilowatt-hour equals 3.6 million joules or 3,600 kilojoules. This is the amount of energy consumed when a 1,000-watt device runs for one hour.

Energy Converter – joules, calories, kWh

Energy Converter

Convert energy measurements between joules, calories, BTU, kilowatt-hours, and more.

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Complete List of Energy Units for Conversion

Understanding energy units

The joule (J) is the SI unit of energy, defined as the amount of work done when a force of one newton acts through a distance of one meter. Energy measures the capacity to perform work or produce heat.

Common energy relationships

1 joule = 1 newton-meter (N·m)
1 kilocalorie = 4,186.8 joules
1 BTU (British Thermal Unit) ≈ 1,055.06 joules
1 kilowatt-hour (kWh) = 3,600,000 joules
1 electronvolt (eV) ≈ 1.602 × 10⁻¹⁹ joules

Common energy applications

Joules are used in physics and engineering for scientific calculations. Calories are used in nutrition to describe food energy content (where 1 food calorie = 1 kilocalorie). Kilowatt-hours are used to measure electricity consumption. BTUs are used in HVAC systems and heating applications. Electronvolts are used in atomic and nuclear physics.

Energy conversion accuracy

Energy conversions use exact relationships defined by the International System of Units and NIST standards. The conversion factors are based on fundamental definitions of work, power, and the joule.

Frequently Asked Questions

What is the difference between joules and calories?: A joule is the SI unit of energy, while a calorie (or kilocalorie in nutrition) is an older unit. 1 kilocalorie equals 4,186.8 joules. Food energy is typically measured in kilocalories (often labeled as "Calories" with a capital C).
How much energy does 1 kWh represent?: 1 kilowatt-hour equals 3.6 million joules or 3,600 kilojoules. This is the amount of energy consumed when a 1,000-watt device runs for one hour.