Calorimeter, an instrument for measuring the amount of heat released or absorbed in physical and chemical processes. Calorimeters are of many types. They are used to determine the heat content, specific heat, latent heat, and other thermal properties of substances. Calorimeter readings are usually taken in calories or British thermal units (Btu).

The bomb calorimeter is a common type used to determine the heat of combustion of such substances as fuel and food. The substance to be tested is burned in a metal chamber that is placed in a well-insulated vessel of water. Heat generated by the burning is transferred to the water. The increase in temperature of the water and the measured weights of both the substance and the water are used to determine the heat released by the substance.