Calories to BTU Converter

ConversionEdited by Hemant Kumar and Anjita Rai, founders · How we checkUpdated Free · No sign-up

Quick answer: To convert calories to BTU, multiply by 0.003965667. For example, 10 cal is 0.03965667 Btu. One calorie equals 0.003965667 Btu.

Use the Calories to BTU Converter

Calories to BTU formula and what each symbol means

Btu = cal × 0.003965667

Symbols used in the formula
SymbolMeaning
calCalorie
BtuBritish thermal unit

Calories to BTU examples

1 cal

1 cal × 0.003965667 = 0.003965667 Btu.

10 cal

10 cal × 0.003965667 = 0.03965667 Btu.

100 cal

100 cal × 0.003965667 = 0.3965667 Btu.

Calories compared with BTU

One Btu is 252.2 times as large as one cal, so your number gets smaller when you convert calories to BTU and bigger when you convert back. If the answer is not smaller than what you typed, you multiplied instead of dividing.

About calories and BTU

Calorie (cal): The thermochemical calorie, exactly 4.184 joules. British thermal unit (Btu): International Table British thermal unit, 1,055.05585262 joules.

Where calories to BTU conversions are used

Food labels show kilocalories or kilojoules, and electricity bills use kilowatt-hours. Gas and heating are often billed in therms, BTU or megajoules.

How to calculate Calories to BTU step by step

  1. Enter the value in cal (the starting unit).
  2. Multiply by 0.003965667, because 1 cal = 0.003965667 Btu.
  3. The product is the value in Btu. To go back, divide by 0.003965667 or multiply by 252.1644.

Popular energy conversions

How to read your Calories to BTU result

Quick estimate: multiply by about 0.004 to get BTU from calories; this is within 0.9% of the exact factor. Food labels use the kilocalorie (kcal, written Calorie in the US), electricity bills use the kilowatt hour, and heating uses the Btu.

CALORIESBTU
10.003965667
20.007931334
50.01982833
100.03965667
200.07931334
500.1982833
1000.3965667
1,0003.965667

BTU to Calories: quick table

BTUCALORIES
1252.1644
51,260.822
102,521.644
256,304.11
5012,608.22
10025,216.44
25063,041.1
500126,082.2

Common mistakes when calculating Calories to BTU

  • Mixing the small calorie (cal) with the food Calorie (kcal): the difference is a factor of 1,000.
  • Dividing when you should multiply: from cal to Btu multiply by 0.003965667; from Btu to cal divide by 0.003965667.

Calories to BTU FAQ

How many Btu are in 1 cal?

1 cal equals 0.003965667 Btu.

How many cal are in 1 Btu?

1 Btu equals 252.1644 cal.

Is 1 cal = 0.003965667 Btu an exact conversion?

Yes. The calorie and the british thermal unit are both defined exactly in SI terms, so the ratio has no measurement uncertainty; 0.003965667 is just that ratio shown to 7 significant figures.

What is a calorie (cal)?

The thermochemical calorie, exactly 4.184 joules.

How can I estimate calories to BTU in my head?

Quick estimate: multiply by about 0.004 to get BTU from calories; this is within 0.9% of the exact factor.

What is 15 cal in BTU?

15 cal = 0.059485 Btu (since 15 × 0.003965667).

What is 75 cal in BTU?

75 cal = 0.297425 Btu (since 75 × 0.003965667).

What is 300 cal in BTU?

300 cal = 1.1897 Btu (since 300 × 0.003965667).

How many decimals should I keep when converting cal to Btu?

Match the precision of your original measurement. For example, 0.03965667 Btu rounds to 0.0397 Btu at 3 significant figures; keep more digits only for engineering or scientific work.

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Method, review and disclaimer

Edited by: Hemant Kumar and Anjita Rai, founders of ToolsVault (SEO and content professional, not a licensed adviser). Method: this tool runs in your browser using the formula shown on this page; the numbers you enter are not sent to our servers. Sources: NIST SP 811, Appendix B.8: conversion factors