Heat is one of the many forms of energy and it is measured in Joules.
If you want to measure the amount of heat needed to heat an object, you could use the followings as refference: 1 gram of water is heated to 1 Celsius degree. The amount of heat needed is of 4.2 Joules.
If you want to determine how many Joules are needed to heat 1 kg of water to 10 Celsius degrees, you'll have to use the rule of three.
1g water........1C degree...............4.2 Joules
1000 g...........10C degrees.............x Joules
We also know that 4.2 Joules are equivalent to one calorie.
If you want to determine how many Joules are needed to transform the mass of a substance from a liquid to a gas, you'll have to use the formula:
Q = mCdeltaT
m - themass of the substance
C- the specific heat of the substance
delta T - the change in temperature (T final-Tinitial)