Is a food Calorie the same as a calorie?

No. The Calorie on nutrition labels is actually a kilocalorie, equal to 1000 small calories or 4184 joules. So a 200 Calorie snack contains 200 kcal, which is 836,800 joules of food energy.

How many joules are in a kilowatt-hour?

Exactly 3,600,000 joules (3.6 megajoules), since one watt-hour is 3600 joules and a kilowatt-hour is a thousand of those. This is the unit your electricity bill is measured in.

A British thermal unit is roughly the energy to heat one pound of water by one degree Fahrenheit, about 1055.06 joules in the IT definition. BTUs are common for heating, air conditioning, and appliance ratings.

Why include the electronvolt?

The electronvolt (eV) is the natural energy unit in atomic and particle physics, equal to 1.602176634e-19 joules. It is far too small for everyday use but essential when discussing photon energies or chemical bonds.

How does the converter stay accurate?

Each unit stores an exact joules-per-unit factor. Your value is converted to joules and then divided into the target unit, so every conversion shares one base and avoids compounding rounding error.

Energy Unit Conversion Reference

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Energy crops up in nutrition (Calories), utility bills (kWh), heating (BTU), mechanics (foot-pounds), and physics (electronvolts) — all measuring the same quantity in very different sizes. This reference converts any energy value into every supported unit at once, using exact factors.

How it works

Each unit stores an exact number of joules per unit, with the joule as the SI base. Conversion is two steps:

joules = value × joulesPerUnit[from]
result = joules ÷ joulesPerUnit[to]

The useful anchors are 1 kWh = 3.6 × 10⁶ J, the thermochemical 1 cal = 4.184 J (so the food Calorie = kcal = 4184 J), the IT 1 BTU = 1055.05585262 J, and the physics 1 eV = 1.602176634 × 10⁻¹⁹ J. The mechanical foot pound-force is ≈ 1.3558 J.

Tips and example

A 200-Calorie snack is 200 kcal = 200 × 4184 = 836,800 J ≈ 0.232 kWh of food energy.
To convert household electricity: 1 kWh = 3.6 MJ, so a 2 kWh appliance run uses 7.2 MJ.
The “calorie” on labels is the kilocalorie; a physics-class small calorie is a thousand times smaller, a frequent source of confusion.

Extremely large or small results — such as electronvolts — appear in scientific notation so they remain readable.