Skip to main content
snaptools
Categories json csv text encoding hash formatters converters generators
Guides Pricing Sign in
chain
⇄
Energy Converter
⌃⏎ run · ⎋ clear · / focus input
All units
send result to
no matches
// about this tool

Energy Converter Online

Updated 2026-10-24

Convert energy online for free between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, and BTU. Enter a value, pick the units, and SnapTools shows the result instantly. Everything runs in your browser, so nothing you enter is uploaded.

Energy hides behind several everyday units: food labels in kilojoules or Calories, electricity in kilowatt-hours, heating systems in BTU. A common gotcha is that a food "Calorie" is really a kilocalorie. This converter moves between all of them in any direction using standard factors, so you can compare a snack's energy, read your electricity bill, or size an air conditioner with confidence.

// how to use

  1. 1 Enter an energy value in the input panel.
  2. 2 Choose the unit you're converting from and the unit you're converting to.
  3. 3 Read the converted value on the right, then copy it.

// examples

Kilocalories to kilojoules
Input
100 kcal → kJ
Output
418.4 kJ
Kilowatt-hours to joules
Input
1 kWh → J
Output
3600000 J
BTU to joules
Input
1 BTU → J
Output
1055.06 J

// common uses

Converting food energy between kilocalories and kilojoules Electricity usage between kilowatt-hours and joules HVAC and heating figures in BTU Physics and engineering energy calculations

// faq

Who was the joule named after?
The joule is named after James Prescott Joule, a 19th-century English brewer who ran his family business by day and studied heat and energy in a home laboratory. His experiments measuring how falling weights heat water through friction established the mechanical equivalent of heat, earning him the SI energy unit.
Which energy units are supported?
Joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, and BTU, with conversion in any direction.
Are food "calories" the same as calories here?
The Calorie on nutrition labels is actually a kilocalorie (kcal). So a 250-Calorie snack is 250 kcal, which is about 1046 kJ; use the kcal unit for food energy.
How many joules are in a kilowatt-hour?
Exactly 3,600,000 J (3.6 MJ), since one watt-hour is 3600 joules. This is the unit your electricity meter uses, and it converts directly here.
What is a BTU?
The British thermal unit is a unit of heat energy, about 1055 joules, common in heating, cooling, and HVAC specifications. It is fully supported.

// works with your data

Pressure Converter Weight Converter Temperature Converter Time Duration Converter Number to Words Base64 Encoder

Use this via API

Get a free API key → 
curl -X POST https://thesnaptools.com/api/v1/tools/energy-converter \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"value":"100 kcal \u2192 kJ"}'