How many joules are in one calorie?

One small (thermochemical, gram) calorie equals 4.184 joules exactly. This is the calorie used in physics and chemistry, written with a lowercase c.

Is this the same as a food Calorie?

No. A food Calorie (capital C) is a kilocalorie, equal to 1000 small calories, or 4184 J. This tool converts the small calorie at 4.184 J each.

Is anything sent to a server?

No — the conversion runs entirely in your browser and no data is uploaded.

Calories to Joules Converter

Calories to joules — the exact physics conversion

One small calorie equals 4.184 joules exactly. This converter turns the gram-calorie used in physics and chemistry into joules (J), the SI energy unit, and back again.

Be careful not to confuse it with the food Calorie on nutrition labels, which is a kilocalorie (1000 small calories = 4184 J). For lab and textbook work, the small calorie is the right unit — so 100 cal is 100 × 4.184 = 418.4 J.

Choose a direction, enter your number, and the answer updates instantly — all in your browser, with nothing leaving your device.