Work out how much a tank holds, and how much liquid is in it right now. Choose a vertical cylinder, horizontal cylinder or rectangular tank, enter its inside dimensions and, optionally, the depth of the liquid.
In a horizontal cylinder the volume does not rise in step with the level — the tank is wider in the middle — so the calculator uses the exact circular-segment formula.
Formula
Cylinder = π × r² × length · Rectangle = L × W × H
For a horizontal cylinder filled to height h: area = r² × arccos((r − h) ÷ r) − (r − h) × √(2rh − h²), multiplied by the length. 1 US gallon = 231 in³ = 3.785 L.
Worked example
A vertical tank 48 in across and 60 in tall holds π × 24² × 60 = 108,573 in³, or 470 gallons. Lying on its side and half full, the same tank holds 235 gallons.
Frequently asked questions
How do I calculate the volume of a cylinder tank?
Multiply π by the radius squared and by the height (or length). Use inside dimensions for the usable capacity.
Why is a horizontal tank not half full at half its volume until the middle?
The tank is narrowest at the top and bottom, so each inch of level near the middle holds more liquid than an inch near the bottom.
Last updated · Calculations checked by automated tests· Editorial policy