How it works
volume = π × (diameter ÷ 2)² × heightUS gallons = cubic feet × 7.48052
- diameter
- the width across the top, in feet
- height
- how tall the tank is
- 7.48052
- US gallons in a cubic foot
This is for a full upright cylinder. A tank on its side, or a partly filled one, needs a different formula for the fill level.
Frequently asked questions
How do I calculate tank volume in gallons?
Work out cubic feet with π × radius² × height, then multiply by 7.48.
How many gallons in a 6 by 8 ft tank?
About 1,690 US gallons.
How many gallons in a cubic foot?
About 7.48 US gallons.
What if the tank is on its side?
A horizontal tank uses a different formula based on the fill depth, not this upright one.