Cubic feet to US gallons (cu ft to gal)

One cubic foot is exactly 7.48051948 US gallons. The US gallon is defined as exactly 231 cubic inches and a cubic foot is 1,728 cubic inches, so the factor is 1728/231: exact, and a repeating decimal because 231 has a factor of 7.

Worked through: 50 cu ft x 7.48051948 = 374.026 gal.

Going the other way, one US gallon is 0.1336805556 cubic feet.

For mental arithmetic: Multiply by 7.5. That is 0.3% high, which is well inside the error of measuring a pool's average depth.

The pair behind every pool, tank and water bill in the US. A pool's volume comes out of a tape measure in cubic feet (length times width times average depth), and the chemicals are dosed per gallon, so this factor sits in the middle of every pool calculation. Water utilities often bill in CCF or HCF, a hundred cubic feet, which is 748 gallons; a bill that says 6 CCF is about 4,490 gallons. Note that this is the US gallon. A cubic foot is 6.23 imperial gallons, so a British pool figure in gallons is about 17% smaller for the same water.

Precision is worth matching to the input. A measurement given as 1 cu ft carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.