How to use this calculator
Choose the tank shape, enter dimensions in feet, and convert cubic feet to US gallons.
Formula
Rectangular: L × W × H. Cylinder: πr²h.
Example
A 2 × 3 × 4 ft rectangular tank has 24 ft³, approximately 179.53 US gallons.
Frequently asked questions
Are results exact for rounded tank ends?
No. Use the actual tank geometry or manufacturer capacity for non-standard shapes.