About

Energy quantification varies significantly between physics, chemistry, and nutritional science. This discrepancy often leads to critical errors in data interpretation, specifically the confusion between the "small" calorie used in chemistry and the "large" Calorie (or kilocalorie) used on food labels. This tool provides a rigorous conversion method between the SI unit of energy (Joule) and both variants of the calorie.

Understanding the specific heat capacity of water was the historical basis for the calorie, but modern standardization relies on exact definitions. Whether you are a student solving thermodynamic equations or a dietician calculating metabolic equivalents, distinguishing between thermochemical calories and nutritional kilocalories is vital for accuracy. This application adheres to the ISO 80000-5 standard for energy units.

Formulas

The conversion relies on specific defined constants. The most common scientific standard is the thermochemical calorie.

For small calories (cal):

E_cal = E_J4.184

For nutritional calories (kcal):

E_kcal = E_J4184

When converting from Calories to Joules, the operation is inverted (multiplication). Note that 1 kcal = 1000 cal.

Reference Data

Energy Type	Symbol	Joules (J)	Definition / Context
Thermochemical Calorie	cal_th	4.184	Chemistry & Physics (Exact)
International Steam Table Calorie	cal_IT	4.1868	Engineering Steam Tables
Nutritional Calorie (Large)	kcal / Cal	4184	Food Energy Labeling
Kilojoule	kJ	1000	SI Derived Unit
Watt-hour	Wh	3600	Electrical Energy
Electronvolt	eV	1.602×10^-19	Atomic Physics
British Thermal Unit	BTU_ISO	1055.06	HVAC & Heating

Frequently Asked Questions

A "cal" (lowercase) is the amount of heat to raise 1 gram of water by 1°C. A "kcal" (often written as "Calorie" with a capital C on food) is 1,000 small calories. It is the energy to raise 1 kilogram of water by 1°C.

This is the exact definition of the thermochemical calorie. It was originally derived from the specific heat capacity of water at standard conditions but is now a fixed constant to ensure reproducibility in scientific calculations.

While it handles Joules, HVAC often uses BTUs. You can convert Joules to BTUs knowing that 1 BTU is approximately 1055 Joules, but this specific tool focuses on the relationship between metric Joules and Calories.

No. The history log is session-based and designed to help you compare multiple calculations within a single workflow. It clears upon reloading the page.