Cylinder Volume Inches to Gallons Calculator
Convert cylinder inches to gallons using US Gallons = cubic inches divided by 231. For a tank with radius 7 in and height 15 in, volume is 2,309.07 cu in, which divided by 231 yields 9.996 US gallons (8.323 UK gallons). Enter your inch measurements below to calculate gallon volume.
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Finding US gallons from inch measurements
This tool calculates gallon capacity directly from inch dimensions. It is used for custom aquariums, tanks, and cisterns.
The 231 cubic inch per gallon rule
Calculate volume in cubic inches using V = pi r squared h. Then divide by 231 to find US gallons: Gallons = cubic inches divided by 231.
Frequently Asked Questions
How do you manually convert cubic inches directly into US gallons?
Take your final volumetric total in cubic inches (in³) and simply divide it by exactly 231. The resulting quotient is your total physical capacity in US liquid gallons.
How many total cubic inches are physically inside one gallon?
By strict mathematical definition within the United States Customary system, one single liquid gallon requires exactly 231 cubic inches of structural space to exist.
What is the difference between a liquid gallon and a dry gallon?
A standard US liquid gallon equals 231 cubic inches. A traditional US 'dry gallon' (used historically for sizing crops like apples and grains) is roughly 268.8 cubic inches.
How many gallons does a 1,000 cubic inch cylinder hold?
If your total calculated geometry yields a volume of 1,000 cubic inches, dividing by 231 reveals that the tank holds precisely 4.33 US gallons of liquid.
How do I calculate fractional inches into gallons?
You must first convert your fractions into smooth decimals. For a 4 1/2 inch radius, input 4.5 into the calculator, and the script will handle the exact gallon fraction mapping automatically.