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Calories to Kilocalories Converter
↔ Convert kcal to cal instead

Common Conversions

cal kcal
1 0.001
10 0.01
100 0.1
500 0.5
1000 1
2000 2
5000 5
10000 10
50000 50
100000 100
500000 500
1000000 1000

Why this conversion matters in chemistry

Two calories live alongside each other and they differ by a factor of 1000. The small calorie (cal) is the unit physical chemistry uses for specific heats — water at 1 cal/(g·°C), ice fusion at 80 cal/g, water vaporization at 540 cal/g. The dietary Calorie with a capital C is one kilocalorie, the unit on a food label. A 250 Cal snack bar holds 250,000 cal. The thousand-fold gap is the distinction that careful unit conventions exist to manage. Mistaking one for the other introduces a factor of 1000 into a calorimetry calculation, which is most of why SI joules eventually displaced both.

Formula

kcal = cal / 1000

Worked Examples

1000 cal = 1 kcal

The conversion anchor — 1000 small calories per kilocalorie, also one dietary Calorie.

80000 cal = 80 kcal

The heat of fusion of one kilogram of ice — water at 80 cal/g times 1000 g.

540000 cal = 540 kcal

The heat of vaporization of one kilogram of water at 100 °C — about seven times the energy of melting the same mass of ice.

68310 cal = 68.31 kcal

The heat released when one mole of hydrogen burns to liquid water — the H₂ combustion enthalpy in legacy kcal units (−285.83 kJ/mol in modern SI).

Frequently Asked Questions

How do I convert calories to kilocalories?
Divide by 1000. The relationship is exact, so 5000 cal becomes precisely 5 kcal with no rounding.
What's the difference between cal, Cal, and kcal?
A small calorie (cal) is 4.184 J. A food Calorie (Cal, capital C) is one kilocalorie, which is 1000 cal = 4184 J. The capital C carries a thousand-fold meaning, which is most of the source of confusion in nutrition versus chemistry calculations.
Why does this distinction matter in chemistry?
Mixing cal and kcal in a calorimetry calculation drops the answer by a factor of 1000. Specific heats and q = mcΔT typically use cal/(g·°C); thermodynamic tables sometimes use kcal/mol. The unit notation is what keeps the two from quietly colliding.
What does 'Calorie' mean on a food label?
A capital-C Calorie equals one kilocalorie. A 200 Calorie snack provides 200 kcal — equivalently 200,000 small calories or 836.8 kJ. The capitalization on the label is the convention that's supposed to prevent the thousand-fold confusion, even if it rarely succeeds in practice.