If by "lpg" you mean litres/kg and are talking about water at standard temperature and pressure:

1 cc (cubic centimeter) = 1 ml (milliliter) = 1 gram

1000 cc = 1000 ml = 1 litre = 1000 grams = 1 kilogram

Ergo, 1 ltr = 1 kg or 1 litre/1000 grams or 1000 milliliters/gram

If by "lpg" you mean liquid propane gas:

1 cubic meter of lpg at -40 degrees C of F weighs 583.07 kilograms

1 cubic meter = 1,000 litres = 1,000,000 ml

583.07 kg =587,070 grams

Whether you divide 1000 liters/587.07 kg or 1,000,000 ml/587,070 grams the answer is 1.71505994134 litres/kg or ml/g for liquid propane gas

1 cc (cubic centimeter) = 1 ml (milliliter) = 1 gram

1000 cc = 1000 ml = 1 litre = 1000 grams = 1 kilogram

Ergo, 1 ltr = 1 kg or 1 litre/1000 grams or 1000 milliliters/gram

If by "lpg" you mean liquid propane gas:

1 cubic meter of lpg at -40 degrees C of F weighs 583.07 kilograms

1 cubic meter = 1,000 litres = 1,000,000 ml

583.07 kg =587,070 grams

Whether you divide 1000 liters/587.07 kg or 1,000,000 ml/587,070 grams the answer is 1.71505994134 litres/kg or ml/g for liquid propane gas