Calories to British Thermal Units Converter

One Calorie equals 0.003965666831 British Thermal Units (1 cal = 0.003965666831 BTU). Multiply a Calorie value by 0.003965666831 to get the equivalent in British Thermal Units. The calculator is above; the formula and worked examples are below.

Formula

BTU = cal × 0.003965666831

Multiply the Calorie value by 0.003965666831 to get the equivalent value in British Thermal Units.

Example Conversions

1 Calorie (cal)

0.003965666831 British Thermal Unit (BTU)

5 Calorie (cal)

0.01982833416 British Thermal Unit (BTU)

10 Calorie (cal)

0.03965666831 British Thermal Unit (BTU)

25 Calorie (cal)

0.09914167078 British Thermal Unit (BTU)

100 Calorie (cal)

0.3965666831 British Thermal Unit (BTU)

Conversion Table

Common conversion values from Calorie to British Thermal Unit
Calorie (cal)British Thermal Unit (BTU)
0.10.0003965666831
0.50.001982833416
10.003965666831
20.007931333663
50.01982833416
100.03965666831
250.09914167078
500.1982833416
1000.3965666831
2500.9914167078
5001.982833416
10003.965666831

How to Convert Manually

Use these steps to convert Calorie values to British Thermal Unit without the calculator.

  1. Write down the value in Calorie (cal) that you want to convert.
  2. Multiply that value by 0.003965666831.
  3. For example, 10 Calories × 0.003965666831 = 0.03965666831 British Thermal Units.
  4. Label the result as British Thermal Unit (BTU).

Relative Size Comparison

1 Calorie
1 British Thermal Unit252.1644007 Calories
1 BTU

This chart shows the visual difference in size between exactly one Calorie and one British Thermal Unit.

About Calorie and British Thermal Unit

The calorie (small calorie) is exactly 4.184 joules under the thermochemical convention. It originally described the heat to warm one gram of water by 1 °C. Chemistry uses it; food 'Calories' are actually kilocalories. The British thermal unit is about 1,055.06 joules, the heat to raise one pound of water by 1 °F. US heating and cooling equipment is rated in BTU per hour. One Calorie equals 0.003965666831 British Thermal Units (1 cal = 0.003965666831 BTU). Calorie is used in chemistry heat calculations and in scientific literature. British Thermal Unit is used in air conditioner and furnace ratings in the US.

Precision and Rounding:Energy factors mix exact definitions (1 kWh = 3,600,000 J; 1 cal = 4.184 J thermochemical) with measured conventions (1 BTU ≈ 1,055.056 J). Nutrition and utility bills round to whole units; engineering heat calculations should keep the full factor until the final step.

Conversion factors per NIST Special Publication 811 and the BIPM SI Brochure (9th edition) (reference).

Worked Example

15Calories equals0.05948500247British Thermal Units.

15 cal × 0.003965666831 = 0.05948500247 BTU

FAQ

How do I convert Calorie to British Thermal Unit?

Multiply the Calorie value by 0.003965666831 to get the equivalent value in British Thermal Units.

What is the formula for Calorie to British Thermal Unit?

The formula is BTU = cal × 0.003965666831.

How many British Thermal Units are in 1 Calorie?

1 Calorie equals 0.003965666831 British Thermal Units.

Can I convert British Thermal Unit back to Calorie?

Yes. 1 British Thermal Unit equals 252.1644007 Calories, and the related converter can reverse the calculation.

What are common names for Calorie and British Thermal Unit?

Calorie is shown as cal and may also be searched as calorie, calories, small calorie. British Thermal Unit is shown as BTU and may also be searched as btu, british thermal unit.

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