An empty is rare to overfill, as you know what kg would contain inside the specific gas cylinder bottle. The Calor gas bottle comes with 80% cut off valve, allowing 20% of the space for the natural expansion of the LPG (Propane). In other words, they are oversized. Overfilling is extremely likely with gas cylinder bottles. So, the 13.4kg bottle should hold no more than 21.44 litres of LPG from empty. And the 45kg Propane tank can hold no more than 100.2 litres of LPG gas.
Keep in mind that, country like in the UK Calor gas is one of the two main Propane distributors. They offer different bottle sizes and shape. Calor gas has a broad range of sizes like 4.5kg and 7kg. Propane users have the choice of 3.9kg, 6kg and 13kg. However, this may be a different case scenario in your country, where only gas plant and local reseller retailers are available.
It is very important to check properly for technical information of your gas cylinder bottles. Some gas cylinders have great information to help you. This is stamped on either the neck or bottom ring dimensions of every gas cylinder bottles. Some even have the tare worth, litres painted on them and other valuable information.
List Of Gas Cylinder Bottles Kg's And Litres
KG Litres
3.9kg 7 litres
6kg 10 litres
13kg 28 litres
19kg 45 litres
45kg 100 litres
LPG: 1kg = ~2 litres
Conversion of LPG kg to litre
= 1kg - 1.96L