Energy ConverterConvert between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, and electronvolts.
Energy Converter
Convert between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, and electronvolts.
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What Is Energy Converter?
An energy converter translates between different units of energy and work. The joule (J) is the SI unit of energy, defined as the work done by a force of one newton over one meter. Calories are used in nutrition (1 food calorie = 1 kilocalorie = 4,184 joules). Kilowatt-hours measure electrical energy consumption. BTUs (British Thermal Units) are common in HVAC and heating systems. Electronvolts are used in particle physics and quantum mechanics. This converter supports eight energy units spanning from subatomic physics to household electricity billing, providing exact conversions based on internationally defined values.
Why Use Our Energy Converter?
- Covers eight energy units across science, nutrition, and engineering.
- Exact conversion using SI-defined factors.
- Essential for electricity bills, nutrition labels, and scientific work.
- Real-time bidirectional conversion.
- Reference table for common energy equivalences.
Common Use Cases
Nutrition
Convert between calories and kilojoules on food labels.
Electricity
Convert kilowatt-hours to joules or BTUs for energy analysis.
HVAC
Convert BTUs to watts for heating and cooling system comparisons.
Physics
Convert between joules, electronvolts, and other units in research.
Technical Guide
The joule (J) is the SI unit of energy. Key definitions: • 1 calorie (thermochemical) = 4.184 J exactly • 1 kilocalorie ("food calorie") = 4,184 J • 1 watt-hour = 3,600 J (1 W × 1 hour) • 1 kWh = 3,600,000 J = 3.6 MJ • 1 BTU = 1,055.06 J (International Table BTU) • 1 eV = 1.602176634 × 10⁻¹⁹ J (exact since 2019 SI redefinition) The kilowatt-hour is the standard billing unit for electricity. One kWh is the energy consumed by a 1,000-watt appliance running for one hour. A typical US household uses about 900 kWh per month. The BTU was originally defined as the energy needed to raise one pound of water by one degree Fahrenheit. The International Table BTU is now defined as exactly 1,055.05585262 J.
Tips & Best Practices
- 1Food "calories" are actually kilocalories (kcal). 1 food Calorie = 1 kcal = 4.184 kJ.
- 21 kWh = 3,412 BTU. This is useful for comparing electric and gas heating costs.
- 3Your electricity bill is in kWh. Multiply kWh by your rate (¢/kWh) to get cost.
- 4The electronvolt is incredibly small: 1 J = 6.242 × 10¹⁸ eV.
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Unit ConvertersFrequently Asked Questions
QHow many calories in a kilojoule?
QWhat is a kilowatt-hour?
QHow do BTU relate to watts?
QWhat is the difference between calories and kilocalories?
QWhat is an electronvolt?
About Energy Converter
Energy Converter is a free online tool from FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration required. No ads. Just fast, reliable tools.