Is the Energy Converter free?

Yes — the Energy Converter is completely free, with no account, subscription, signup, or usage limits.

Is my data uploaded or stored?

No. The Energy Converter processes everything locally in your browser. Your input is never uploaded, saved, or shared with any server.

Does the Energy Converter work offline?

Yes. Once the page has finished loading, the Energy Converter works without an internet connection.

Which browsers does the Energy Converter work in?

The Energy Converter works in all modern browsers, including Chrome, Firefox, Safari, and Edge — no plugins or extensions needed.

What is 1 food calorie in joules?

1 food calorie (kilocalorie, kcal) = 4,184 J = 4.184 kJ. Food labels typically list kcal, not cal.

Energy Converter

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

From

Joule (J)

0.001

Kilojoule (kJ)

1 J = 0.001 kJ

All Conversions for 1 J

Kilojoule	kJ	0.001
Megajoule	MJ	0.000001
Calorie	cal	0.2390057361
Kilocalorie (kcal)	kcal	0.0002390057361
Watt-hour	Wh	0.0002777777778
Kilowatt-hour	kWh	2.777778e-7
Electronvolt	eV	6.241496e+18
BTU	BTU	0.0009478133945
Foot-pound	ft·lb	0.7375610332

Free browser-based tool · Runs 100% on your device · Last updated July 7, 2026

What is the Energy Converter?

The free Energy Converter covers 10 units: joules (J), kilojoules (kJ), megajoules (MJ), calories (cal), kilocalories (kcal), watt-hours (Wh), kilowatt-hours (kWh), electron volts (eV), British Thermal Units (BTU), and foot-pounds (ft·lb). Enter an energy value, select source and target units, and convert instantly. The All Conversions table displays all 10 units at once for scientific, nutritional, and engineering reference.

→ Converting kcal to kJ for international nutrition label reading
→ Converting kWh to MJ for energy billing or solar panel output
→ Converting BTU to kJ for HVAC system specifications
→ Converting joules to eV for particle physics or semiconductor work

How to Use the Energy Converter

1 Select the source energy unit (e.g. kcal) from the From dropdown.
2 Enter the energy value in the input field.
3 Choose the target unit (e.g. kJ) from the To dropdown.
4 View the instant conversion result.
5 Click ⇄ Swap to reverse direction.
6 See every unit in the All Conversions table.

Key Features

⚡
10 energy units

Spans nutrition (cal, kcal), electrical (Wh, kWh), physics (J, eV), and engineering (BTU, ft·lb).
🍎
Nutrition and food science

Convert food calories (kcal) to kJ for international nutrition label comparison.
🔋
Electrical energy

Wh and kWh support for battery, solar panel, and energy billing calculations.
📊
All Conversions table

Full-spectrum view of all 10 energy units at once.
🆓
Free, no registration

Works entirely in-browser with no account required.

Example Usage

Example Input

From: kcal · Value: 2000 · To: kJ

Example Output

2000 kcal = 8,368 kJ

Frequently Asked Questions about the Energy Converter

What is the Energy Converter?: The Energy Converter is a free online tool that lets you convert between joules, calories, kilowatt-hours, BTU, and more. It runs entirely in your browser, so there is nothing to install and nothing is uploaded to a server.
Is the Energy Converter free?: Yes — the Energy Converter is completely free, with no account, subscription, signup, or usage limits.
Is my data uploaded or stored?: No. The Energy Converter processes everything locally in your browser. Your input is never uploaded, saved, or shared with any server.
Does the Energy Converter work offline?: Yes. Once the page has finished loading, the Energy Converter works without an internet connection.
Which browsers does the Energy Converter work in?: The Energy Converter works in all modern browsers, including Chrome, Firefox, Safari, and Edge — no plugins or extensions needed.
What is 1 food calorie in joules?: 1 food calorie (kilocalorie, kcal) = 4,184 J = 4.184 kJ. Food labels typically list kcal, not cal.