1 kg of natural gas = how many litres of petrol?

Answer 1

Although Natural Gas in its raw state directly from a gas well or by extraction from Crude oil, does contain some of the elements of gasoline up to some Pentanes and heavier, together with water vapour;... All except Methane, Ethane and a small amount of Propane is removed when the gas is compressed, cooled and separated from the water.
The removed 'heavy' compounds may be further processed as Naphtha components but, the amount of gasoline components will be very small and not likely to be considered.
More often these components will go to a fuel system for plant use in furnaces and boilers.

(Natural Gas is not merely Methane even when Liquefied to LNG. Some Ethane and Propane is desirable to maintain a reasonable Heating Value of the product).

Answer 2

Natural gas i.e. methane is not used to make petrol (gasoline). Gasoline is culled from crude oil sources. Methane is used as fuel for homes for heating and appliances like stoves.

There are other petroleum gasses used for fuel. You can read about them here. http://en.wikipedia.org/wiki/Liquified_petroleum_gas. In America though, natural gas usually refers to methane.

http://en.wikipedia.org/wiki/Gasoline

Answer 3

Natural gas can produce anywhere from 700 to 2470 BTU/Cu.Ft., at std. conditions.

Gasoline will produce from 126,000 to 129,000 BTU/gallon

If you are looking to compare the two, I'll leave the calcs to get to Kg. and Liters up to you.