its 7.48 gallons of water per cubic foot, so calculate your cubic feet then times it by 7.48, but dont forget that that is in cubic FEET, not inches, plugging in the numbers given will give you cubic inches, the best thing to do is to convert the 6" into feet, then do your calculations
A 72-inch pipe 16 feet long holds up to 3,384.1 US gallons of water.
111 gallons of water.
14.7 gallons of water.
12,239.9 gallons of water per 3,000 feet.
5.5 gallons per 15 feet of 3-inch pipe.
1.6 gallons of water.
6.5 US gallons of water.
Up to 1,795.2 gallons of water.
65.3 gallons or 8.7 cubic feet.
40.8 gallons of water per 10 feet of length.
This pipe will hold 1,468.8 gallons of water.
45.9 US gallons.