For each context of the calorie, there exists a unit, the Calorie, that is by definition $1000$ times the value. Therefore, a Calorie is a kilocalorie.

A 15 degree Celsius or 20 degree Celsius calorie is approximately the amount of energy required to raise the temperature of $1$ gram of water by $1$ degree Celsius to 15.5 or 20.5 degrees Celsius, respectively.

A thermochemical calorie is defined as $4.184$ joules.

A International Table calorie is defined as $4.1868$ joules.

A mean calorie is $\frac{1}{100}$ the energy required to raise the temperature of $1$ gram of water from $0$ degrees Celsius to $100$ degrees Celsius, and is approximately $4.19002$ joules.

A 39 degree Fahrenheit, 59 degree Fahrenheit, or 60 degree Fahrenheit calorie is the approximate amount of energy required to raise the temperature of $1$ pound of water by $1$ degree Fahrenheit to 39.5, 59.5, or 60.5 degrees Fahrenheit, respectively.

A thermochemical British thermal unit is defined by the relationship: $1$ thermochemical British thermal unit per pound degree Fahrenheit equals $1$ thermochemical kilocalorie per kilogram kelvin.

A International Table British thermal unit is defined by the relationship: $1$ International Table British thermal unit per pound degree Fahrenheit equals $1$ International Table kilocalorie per kilogram kelvin.

A mean British thermal unit is $\frac{1}{180}$ the energy required to raise the temperature of $1$ pound of water from $32$ degrees Fahrenheit to $212$ degrees Fahrenheit.

For the thermochemical, International Table, and mean contexts, there are the following associated units.

A therm is defined as $10000.$ British thermal units.

A quad is defined as $1.\times {10}^{15}$ British thermal units.

A Q unit is defined as $1.\times {10}^{18}$ British thermal units.

A 15 degree Celsius or 20 degree Celsius heat unit is the approximate amount of energy required to raise the temperature of $1$ pound of water by $1$ degree Celsius to 15.5 or 20.5 degrees Celsius, respectively.

A International Table Celsius heat unit is defined by the relationship: $1$ International Table Celsius heat unit per pound equals $1$ International Table kilocalorie per kilogram.

A thermochemical Celsius heat unit is defined by the relationship: $1$ thermochemical Celsius heat unit per pound equals $1$ thermochemical kilocalorie per kilogram.

A mean Celsius heat unit is $\frac{1}{100}$ the energy required to raise the temperature of $1$ pound of water from $0$ degrees Celsius to $100$ degrees Celsius.