How many kilograms of liquefied gas is 50 cubic meters of natural gas equal to?

How many kilograms of liquefied gas is 50 cubic meters of natural gas equal to?

The calorific value of natural gas is 36mj / m3, that is, 50 * 36 = 1800mj
The calorific value of LPG is 41mj / kg,
Then 50 cubic meters of natural gas is equal to (1800 / 41 =) 43.9 kg