Answer:
576/77 ≈ 7.48052 gal/ft³
Explanation:
You want to know how to calculate gallons per cubic foot.
Volume ratio
The volume of a US gallon is 231 cubic inches, exactly. The volume of a cubic foot is (12 in)³ = 1728 in³. Then the number of gallons in a cubic foot is ...
(1728 in³/ft³)/(231 in³/gal) = 1728/231 gal/ft³ = 576/77 gal/ft³
= 7 37/77 gal/ft³ ≈ 7.480519... (6-digit repeating decimal) gal/ft³
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Additional comment
The Imperial Gallon is defined as 4.54609 liters, so will be fewer per cubic foot. That's approximately 277.419 cubic inches. (The exact fraction has a very long repeat.)