A (small) calorie is a thermochemical unit of heat energy equal to 4.184 joules, historically the energy needed to raise 1 gram of water by 1°C.
Calories to Btu
Convert Calorie (cal) to British thermal unit (BTU) instantly with an exact formula, conversion table, and FAQ.
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Convert calories (cal) to btu (BTU) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
The British thermal unit (BTU) is the energy needed to raise one pound of water by one degree Fahrenheit, widely used for heating and air-conditioning ratings.
BTU = cal × 0.003965666831
Results update instantly for Calories to Btu conversions.
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Formula
BTU = cal × 0.003965666831
cal = BTU × 252.1644007
Conversion table
| 1 cal | 0.003966 BTU |
| 5 cal | 0.019828 BTU |
| 10 cal | 0.039657 BTU |
| 20 cal | 0.079313 BTU |
| 50 cal | 0.198283 BTU |
| 100 cal | 0.396567 BTU |
| 500 cal | 1.982833 BTU |
| 1000 cal | 3.965667 BTU |
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How the formula works
Both calorie and british thermal unit measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in calories by 0.003965666831 to get btu. To reverse the conversion, multiply a british thermal unit value by 252.1644007 to get back to calories.
Frequently asked questions
What is Calorie (cal)?
A (small) calorie is a thermochemical unit of heat energy equal to 4.184 joules, historically the energy needed to raise 1 gram of water by 1°C.
What is British thermal unit (BTU)?
The British thermal unit (BTU) is the energy needed to raise one pound of water by one degree Fahrenheit, widely used for heating and air-conditioning ratings.
How do I convert calories to btu?
Multiply the calorie value by 0.003965666831 to get the equivalent in btu. For example, 5 cal × 0.003965666831 = 0.019828 BTU.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 0.003965666831 is an exact, non-rounded value.
Can I convert btu back to calories?
Yes. Divide the british thermal unit value by 0.003965666831, or multiply it by 252.1644007, to get calories.
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About converting calories to btu
A (small) calorie is a thermochemical unit of heat energy equal to 4.184 joules, historically the energy needed to raise 1 gram of water by 1°C. The British thermal unit (BTU) is the energy needed to raise one pound of water by one degree Fahrenheit, widely used for heating and air-conditioning ratings.
Use this calculator to move between calories and btu accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.