Convert calories to BTU

1 cal=0.003966BTU

Use the converter below to change any calories value into BTU instantly — with formula, conversion table, and real-world examples.

You have

Equals

0.0039657

Conversion formula

Forward

BTU = calories × 0.003966

Reverse

calories = BTU × 252.164

Example: 10 cal × 0.003966 = 0.03966 BTU.

About both units

From

Calorie

cal

The gram calorie (small calorie) equals 4.184 joules — the energy to raise 1 g of water by 1 °C. It is a scientific unit, distinct from the nutrition "Calorie" (kcal). Largely replaced by joules in modern science.

Real-world: Raising 1 g of water 1 °C: 1 cal. A 100 kcal snack = 100,000 small calories.

Read full calorie reference →

British Thermal Unit

BTU

The British Thermal Unit equals approximately 1055 joules — the energy to raise 1 pound of water by 1 °F. Used for HVAC, heating, and air-conditioning capacity in the US. A 9000 BTU/h AC is a small room unit.

Real-world: Window AC: 5000–12,000 BTU/h. Central AC: 24,000–60,000 BTU/h. Home furnace: 60,000–100,000 BTU/h.

Read full british thermal unit reference →

Calorie to British Thermal Unit conversion table

Common calories to BTU values for quick reference.

Calorie (cal)	British Thermal Unit (BTU)
1 cal	0.003966 BTU
10 cal	0.03966 BTU
100 cal	0.3966 BTU
500 cal	1.98283 BTU
1,000 cal	3.96567 BTU
5,000 cal	19.8283 BTU
10,000 cal	39.6567 BTU
50,000 cal	198.283 BTU
100,000 cal	396.567 BTU
500,000 cal	1,982.83 BTU

Tips & common mistakes

Quick tips

1 cal = 4.184 J. 1 kcal = 4184 J.
Scientific "calorie" and nutrition "Calorie" differ by 1000×.
Prefer joules in modern scientific writing.

Avoid these

Assuming "calories" on food labels means gram calories — they are kcal.
Mixing gram calories and kilocalories in calculations.
Confusing calorie (energy) with calorimeter (apparatus).

Frequently asked questions

How many BTU in a calorie?

One calorie equals 0.003966 BTU.

How do I convert calories to BTU?

Multiply the calorie value by 0.003966 to get the equivalent in BTU.

What is 100 calories in BTU?

100 calories equals 0.3966 BTU.

Is a calorie bigger than a british thermal unit?

No. 1 calorie equals 0.003966 BTU, so one calorie is smaller.

How to convert calories to BTU without a calculator?

Multiply by 0 for a quick estimate; use a calculator for precise results.

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