Perhaps the greatest challenge lies precisely in the technical impossibility to translate Giga-calorie in cubic feet or back. It is absolutely different physical quantities: one is the measurement of thermal energy, the other volume, and, suggests a basic physics course, they are not comparable. The task of the consumer of utilities in the end is to calculate the ratio of the amount of heat and volume of hot water consumed.
In order not to get confused, you should start with the definition of the calculated values. Thus, under the understand calorie the amount of heat necessary for heating by 1°C one cubic centimeter of water. In Gcal billion calories in a cubic meter is a million inches, therefore to heat by 1°C one cubic meter of water, you need a 0,001 Gcal.

Considering that hot water should not be colder than 55°C, and cold water enters at 5°C, it is obvious that you will need to heat it to 50°C, that is, to spend on each cubic meter of 0.05 Gcal of heat energy. In the sphere of tariffs of housing and communal services operates a slightly higher ratio of heat consumption for heating one cubic meter of water – 0,059 Gcal, it is connected with the heat losses that occur during transportation of water through pipelines.
Then everything is simple, the heat consumption according to the readings of the counter divide by the number of tenants. Get thus the heat consumption of each tenant, and dividing the resulting figure by the standard 0,059 - the amount of hot water in cubic meters, which must be paid by each tenant. The only subtlety in this calculation is the need to subtract from it, those residents who have installed meters in the apartment.
Consider the calculation for example: flow obsidianovom at the counter was 30 Gcal that tenants who are domestic meters, spent a total of 35 m3 of hot water, tenants without metering devices in the house – 75 people.

35*0,059 = 2,065 is the amount of heat consumed by residents, which are metering devices;
30-2,065 = 27,935 Gcal – the remainder of the expense to other tenants;
27,935/75 = 0,372 Gcal heat consumption per occupant;
0,372/0,059 = of 6.31 m3 of hot water will be invoiced to each tenant, one of those whose apartments are not equipped with metering devices.