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Energy Converter
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// about this tool

Energy Converter Online

Updated 2026-08-19

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

Is my input uploaded to a server?
No. The conversion runs entirely in your browser, so nothing you enter leaves your machine.
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.

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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"}'