Calculate water volume for rectangular, bowfront, and cylindrical aquariums in gallons and liters.
This tool takes tank dimensions for a rectangular, bowfront, or cylindrical aquarium and returns water volume in both US gallons and liters. Rectangular tanks use length times width times height divided by 231 cubic inches per gallon; cylindrical tanks use the circle-area formula times height; bowfront uses a rectangular base plus an allowance for the curved front panel. The number most people misread: it reports the geometric volume of the box, not the actual water you'll pour in, which is always less once substrate, decorations, and the unfilled space below the rim are accounted for.
A concrete input and expected output from the current implementation.
Input
Rectangular tank: length 24 in, width 12 in, height 16 in
Expected output
19.95 US gallons (75.51 liters)
24 x 12 x 16 = 4,608 cubic inches; divided by 231 cubic inches per gallon gives 19.95 gallons, and 4,608 cubic inches x 0.0163871 liters per cubic inch gives 75.51 liters.
Rectangular volume is length x width x height. Cylindrical volume is pi x radius squared x height, using the diameter you enter divided by two. Bowfront volume adds the rectangular back-section volume to an estimate for the curved front bulge, since a true bowfront isn't a simple prism or half-cylinder. Each result is produced in cubic inches or cubic centimeters depending on your chosen unit before conversion.
Once cubic volume is computed, it's converted to US gallons by dividing cubic inches by 231, and to liters by multiplying cubic inches by 0.0163871 (or dividing cubic centimeters by 1000 if you entered metric dimensions). Both gallons and liters display together regardless of which unit you typed in, so you don't need to re-enter figures to see the other.
Use interior dimensions if you can get them, since glass thickness eats into the box's stated size, especially on tanks 40 gallons and up. If you only have the exterior measurements from packaging, expect the real water volume to come in somewhat lower than what the calculator returns.
Manufacturers usually label tanks with a rounded nominal size, like '55 gallon,' based on external dimensions, while this tool computes the exact geometric volume from the numbers you enter. Neither figure equals what you'll actually pour in, since substrate, decorations, and the headspace below the rim reduce it further.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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