A practical capacity calculator for cylindrical or rectangular water, fuel, or storage tanks.
How it works
A cylindrical tank’s volume comes from pi times the radius squared times the length; a rectangular tank’s volume is simply length times width times height. Both are then converted to gallons.
What this does not include
This does not include partially filled tank calculations — this calculator gives the tank’s full capacity, not the volume at a specific fill level.
How to use this calculator
- Choose a tank shape and enter its dimensions.
A worked example
A cylindrical tank with 2 ft radius, 10 ft length: volume = πr²×length = 125.6637 cubic feet.
A rectangular tank 4 × 3 × 2 ft: volume = 24 cubic feet.
What the variables mean
| Variable | Meaning |
|---|---|
| Shape | Cylinder or rectangular tank |
| Radius, length (cylinder) | Cylinder dimensions |
| Length, width, height (rectangular) | Rectangular tank dimensions |
Edge cases worth knowing
Each shape needs completely different inputs — a cylinder’s volume depends on radius and length, a rectangular tank’s on all three linear dimensions, so switching the shape selector changes which fields are actually used.
A radius of zero collapses the cylinder to a line with no volume, so the calculator declines to show a result for that case.
Frequently asked questions
Why does a cylindrical tank use the radius, not the diameter?
The standard cylinder volume formula is built around radius; if you only have a diameter, halve it first to get the radius before entering it.
Is this the same formula as the site’s pipe volume calculator?
Similar cylinder-based math for the cylindrical option, but framed around a standalone tank’s total storage capacity rather than a pipe segment’s flow-through capacity.
What’s a practical use for this?
Sizing a water storage tank, estimating fuel tank capacity, or planning an aquarium or pool’s total volume.
