With this online calculator for calculate gas consumption for heating.
Ratios for a cold winter:
Natural gas consumption per 1 m2 of house area = 3.5 m3/month.
Liquefied gas consumption per 1 m2 of house area = 5.6 liter/month.
Gas consumption by the meter is the amount of gas received by the consumer from the gas supply network and reflected in the gas meter readings.