Energy Converter — Joules, Calories, kWh, BTU & eV

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How to use Energy Converter

Enter the energy value in the “From” field — for example 2000 for 2,000 kcal.
Choose its unit in the first dropdown (Kilocalorie, Kilowatt-hour, BTU…).
Choose the unit you want in the second dropdown — the result appears instantly.
Use the swap button to flip the conversion direction with one click.

What is Energy Converter?

An energy converter translates amounts of energy between units — joules to calories, kilowatt-hours to BTU, or kilojoules to kilocalories. The SI unit is the joule; every other unit is a fixed multiple of it: a calorie is 4.184 J, a watt-hour 3,600 J, a BTU 1,055.06 J, and the electronvolt a tiny 1.602 × 10⁻¹⁹ J used in atomic physics.

The trap to know: the “calorie” on food labels is actually a kilocalorie (kcal) — 4,184 J. So a 500-calorie meal is 500 kcal ≈ 2,092 kJ, which is why European labels showing kJ display numbers about four times bigger than the kcal figure next to them.

About the Energy Converter

This converter covers eight units — joule, kilojoule, calorie, kilocalorie, watt-hour, kilowatt-hour, electronvolt and BTU — converting any pair instantly as you type.

Where it helps: translating a 2,000 kcal daily diet into kilojoules (8,368 kJ) to read EU food labels; converting your electricity bill's kWh into BTU or joules for engineering work; sizing air conditioners, which are still rated in BTU per hour (a 12,000 BTU unit moves 3.517 kW of heat); or converting particle energies between eV and joules in physics homework.

Anchors: 1 kcal = 4.184 kJ, 1 kWh = 3.6 MJ = 3,412 BTU, 1 BTU ≈ 1.055 kJ. Exact factors, computed in your browser.

Frequently Asked Questions

No — a food “Calorie” (capital C) is a kilocalorie: 1,000 small calories = 4,184 J. A 250-calorie snack is 250 kcal ≈ 1,046 kJ, which is the number EU labels print.

Exactly 3,600,000 J (3.6 MJ), because a kWh is 1,000 watts sustained for 3,600 seconds. It is the unit your electricity meter counts.

A British Thermal Unit (1,055.06 J) is the energy to heat one pound of water by 1 °F. US HVAC tradition rates cooling in BTU/h: a typical 12,000 BTU/h window unit equals about 3.5 kW of cooling.

The energy an electron gains crossing one volt: 1.602177 × 10⁻¹⁹ J. Chemistry bonds are a few eV, X-rays are keV, and the Large Hadron Collider reaches TeV — it is the natural unit of the atomic world.

One kWh runs a 10 W LED bulb for 100 hours, boils roughly 10 liters of water, or moves an electric car about 5–7 km. It equals 860 kcal — close to a large meal.