---
title: "Calories to British thermal units — cal to BTU converter"
description: "1 calorie = 0.0039657 British thermal units. Conversion table, the exact formula, and a calculator for any value."
url: https://atoneplace.net/convert/calories-to-btu/
site: "At One Place"
---

# Calories to British thermal units

**1 calorie in British thermal units: 1 cal = 0.0039657 BTU**

BTU = cal × 0.003965666831

To convert calories to British thermal units, multiply by 0.003965666831. The table below gives the values people look up most often, and the converter works for any number.

## Calories to British thermal units table

*Common calorie values converted to British thermal units.*

| Calories | British thermal units |
| --- | --- |
| 1 cal | 0.0039657 |
| 2 cal | 0.0079313 |
| 3 cal | 0.011897 |
| 4 cal | 0.015863 |
| 5 cal | 0.019828 |
| 10 cal | 0.039657 |
| 15 cal | 0.059485 |
| 20 cal | 0.079313 |
| 25 cal | 0.099142 |
| 30 cal | 0.11897 |
| 40 cal | 0.15863 |
| 50 cal | 0.19828 |
| 75 cal | 0.29743 |
| 100 cal | 0.39657 |
| 250 cal | 0.99142 |
| 500 cal | 1.982833 |
| 1,000 cal | 3.965667 |

## How the conversion works

The relationship is BTU = cal × 0.003965666831. Both units measure energy, so the conversion is a fixed factor that never changes.

> Calorie: Thermochemical (small) calorie.

## Common questions

### How many British thermal units are in one calorie?

One calorie equals 0.0039657 British thermal units. BTU = cal × 0.003965666831.

### How do you convert calories to British thermal units?

Use BTU = cal × 0.003965666831. So 10 cal is 0.039657 BTU.

### How many calories are in one British thermal unit?

One British thermal unit equals 252.1644 calories, which is the reverse of the conversion above.

### Is there more than one kind of calorie?

Thermochemical (small) calorie.

## Related pages

- [British thermal units to Calories](https://atoneplace.net/convert/btu-to-calories/)
- [Calories to Joules](https://atoneplace.net/convert/calories-to-joules/)
- [Calories to Kilojoules](https://atoneplace.net/convert/calories-to-kilojoules/)
- [Calories to Kilocalories](https://atoneplace.net/convert/calories-to-kcal/)
- [Calories to Watt-hours](https://atoneplace.net/convert/calories-to-watt-hours/)
- [Calories to Kilowatt-hours](https://atoneplace.net/convert/calories-to-kwh/)

## Sources

- Guide for the Use of the International System of Units (SP 811) — NIST (https://www.nist.gov/pml/special-publication-811) [Public domain (US Government)]
- The International System of Units (SI Brochure) — Bureau International des Poids et Mesures (https://www.bipm.org/en/publications/si-brochure)
- Calculated on this page — At One Place (/about/)