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Tank Volume Calculator
Get the capacity of a cylindrical or rectangular tank in gallons.
Volume
—
US gallons.
| Cubic feet | — |
|---|---|
| Litres | — |
| Shape | — |
| — |
Show our math
Enter your figures above to see the step-by-step working.
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How the Tank Volume Calculator Works
A tank’s capacity is just the volume of its shape. For a cylindrical tank — vertical or lying on its side — that’s π times the radius squared times the length; for a rectangular tank it’s length × width × height. This calculator works in feet and converts the result to US gallons (1 cubic foot = 7.48 gallons) and litres.
Pick the shape, enter the dimensions, and it gives the full capacity. For a partially filled horizontal cylinder the maths is more involved, but the full-tank figure here is what you need for sizing.
gallons = cubic feet × 7.48
Frequently Asked Questions
How do you calculate tank volume?
Find the volume of the shape — πr²h for a cylinder or l×w×h for a box — then convert cubic feet to gallons by multiplying by 7.48.
How many gallons in a cubic foot?
About 7.48 US gallons.
Does tank orientation matter for full volume?
No — a horizontal and vertical cylinder of the same size hold the same amount when full. Orientation only matters for partial fills.
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