Energy Converter
Convert between joules, kilojoules, calories, kilocalories (food Calories), BTU, kilowatt-hours, and watt-hours instantly with all equivalents shown.
Quick Answer
1 kcal = 4.184 kJ. 1 kWh = 3,412 BTU = 3.6 MJ. 1 BTU = 1,055 J. Select units below to convert between 7 energy measurements instantly.
Convert Energy
Enter an energy value and select units.
All Equivalents
| Unit | Value |
|---|---|
| Joules (J) | 3,600,000 |
| Kilojoules (kJ) | 3,600 |
| Calories (thermochemical) (cal) | 860,420.6501 |
| Kilocalories (food) (kcal) | 860.4207 |
| British Thermal Units (BTU) | 3,412.1282 |
| Kilowatt-hours (kWh) | 1 |
| Watt-hours (Wh) | 1,000 |
Energy References
| Example | kJ | kcal |
|---|---|---|
| 1 food Calorie (kcal) Energy in 1 gram of sugar | 4.184 | 1 |
| Snack bar ~200 kcal energy bar | 837.2 | 200.0956 |
| 1 kWh of electricity Running a 100W bulb for 10 hours | 3,600 | 860.4207 |
| Gallon of gasoline ~131 MJ chemical energy | 132,000 | 31,548.7572 |
| Average US daily diet ~2,000 kcal per day | 8,368 | 2,000 |
About This Tool
The Energy Converter provides instant, accurate conversions between seven commonly used energy units spanning scientific, nutritional, and electrical contexts. Whether you are comparing food energy labels, calculating electricity costs, or working on thermodynamics problems, this tool shows all equivalents simultaneously.
Energy in Everyday Life
Energy is measured differently depending on the context. Nutritionists use kilocalories (food Calories), electricians use kilowatt-hours, HVAC technicians use BTUs, and physicists use joules. All measure the same fundamental quantity but at different scales. Understanding how to convert between them helps bridge these disciplines and make informed decisions about energy consumption, diet, and costs.
The Joule as the SI Standard
The joule (J) is the SI unit of energy, defined as the work done when a force of one newton moves an object one meter. Named after physicist James Prescott Joule, it connects mechanical, thermal, and electrical energy in a single coherent unit system. One joule is quite small for everyday use, so kilojoules (kJ) and megajoules (MJ) are more commonly encountered.
Electricity Billing and Energy
Electric utilities bill in kilowatt-hours because it combines power (kilowatts) with duration (hours) in an intuitive way. A 1,500-watt space heater running for 2 hours consumes 3 kWh. At the US average rate of about $0.13 per kWh, that costs approximately $0.39. Understanding kWh helps you estimate appliance running costs and compare energy tariffs effectively.
Frequently Asked Questions
What is the difference between calories and kilocalories?
How do I convert kilocalories to kilojoules?
What is a BTU and where is it used?
How do kilowatt-hours relate to joules?
What is a watt-hour vs a kilowatt-hour?
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