20 liters is around 5.29 U.S. gallons ( VOLUME )
You are missing a measurement to obtain volume. A height it going to be needed.
About 110 liters.
About 177 liters.
7.5 liters is 458 cubic inches.
4.3 liters = 262.4021 cubic inches
There are 286.811597 cubic inches in 4.7 liters.
6 liters = 366.142465 cubic inches
55.1 liters = 3,362.4 cubic inches.
96 cubic inches is 1.573 liters.
8294.4 cubic inches is 135.9 liters.
1.8 liters is 110 cubic inches.
6.6 liters is 402.76 cubic inches.