What is the difference between a calorie and a Calorie?

A lowercase calorie (cal) is a thermochemical unit equal to 4.184 joules. An uppercase Calorie (Cal) — as used in food nutrition — is actually a kilocalorie (kcal), equal to 1000 cal or 4184 joules.

How many joules are in one calorie?

1 thermochemical calorie = 4.184 joules exactly. This is the internationally accepted conversion factor for the thermochemical calorie.

How many joules are in one kilocalorie (food Calorie)?

1 kilocalorie (kcal) = 4184 joules = 4.184 kilojoules. Food labels in the US list Calories which are actually kilocalories.

What is the formula to convert calories to joules?

J = cal × 4.184. For kilocalories: J = kcal × 4184. To go the other way: cal = J ÷ 4.184.

Why does this tool distinguish thermochemical calories from other calorie types?

There are several calorie definitions (thermochemical, IT, 15°C). The thermochemical calorie (4.184 J) is the most common in chemistry and nutrition contexts, so this tool uses it as the standard.

Calories to Joules Converter

Name: Calories to Joules Converter
Availability: InStock
Author: Nham Vu

Enter a value in calories or kilocalories and instantly get the equivalent in joules or kilojoules.

Input

Value Input unit

cal (thermochemical) kcal (food Cal)

Result

Enter a value to see results.

Common Calorie to Joule Conversions

Calories (cal)	Kilocalories (kcal)	Joules (J)	Kilojoules (kJ)
1 cal	0.001 kcal	4.184 J	0.004184 kJ
100 cal	0.1 kcal	418.4 J	0.4184 kJ
1,000 cal	1 kcal	4,184 J	4.184 kJ
2,000 cal	2 kcal	8,368 J	8.368 kJ
10,000 cal	10 kcal	41,840 J	41.84 kJ
100,000 cal	100 kcal	418,400 J	418.4 kJ

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Summary

Enter a value in calories or kilocalories and instantly get the equivalent in joules or kilojoules.

How it works

Enter your calorie value and select the unit (cal or kcal).
The converter multiplies by 4.184 (for cal) or 4184 (for kcal) to get joules.
Kilojoules are calculated by dividing the joule result by 1000.
Results update in real time as you type.
Use the swap button to convert joules back to calories.

Use cases

Convert food energy values from Calories (kcal) to joules for physics or chemistry work.
Check thermochemical energy values in joules for lab calculations.
Convert nutrition data between calorie and joule units for international labeling.
Understand the energy content of foods in SI units.
Quick reference for students studying thermodynamics or nutrition science.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu