π × r² × height, in plain numbers
A cylinder's volume is its circular end area times its length: π × (diameter ÷ 2)² × height. The calculator accepts the diameter in inches or feet, computes cubic feet, and shows yards and gallons — the three units tanks, tubes and round footings get measured in.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- NIST Office of Weights and Measures — the US customary and SI conversion factors used throughout this tool.
- International Code Council — the International Residential Code and International Building Code.
Figures, formulas and reference tables last verified: 19 September 2026.