By Zencalcy Editorial TeamLast reviewed About us
Tank capacity is the inside volume, not the outside, and a tank is never filled to the brim. This calculator handles upright cylinders, rectangular tanks and horizontal cylinders, where the wetted volume for a partly full tank is worth knowing.
Capacity of a cylindrical or rectangular tank.
Cylinder: V = π × r² × h Rectangle: V = L × W × H
Use inside dimensions. A horizontal cylindrical tank only reaches its full nominal capacity when completely full; at half height it holds exactly half. Fill height is measured from the lowest point inside the tank.
| Symbol | Meaning |
|---|---|
| r | Inside radius of a cylinder. |
| L, W, H | Inside dimensions of a rectangular tank. |
π × 2² × 6 = 75.4 cu ft, or 564 gallons (2,135 litres).
Continue with the Pool Calculator, Round Pool Volume Calculator, Pond Calculator, or the Pipe Volume Calculator — or browse more tanks, pools & flow and all construction calculators.
A 4 ft diameter upright cylinder 6 ft tall holds about 564 gallons.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026