Tank Volume Calculator (Gallons, Liters & Partial Fill)
Calculate total and partial liquid capacity in US gallons, liters, and cubic feet for vertical cylinder, horizontal cylinder, and rectangular tanks.
How to Use the Tank Volume Calculator (Gallons, Liters & Partial Fill)
Calculating the storage volume of a water, fuel, chemical, or agricultural tank requires first determining the interior geometric volume in cubic feet (or cubic meters) and then multiplying by the appropriate liquid unit conversion factor. For vertical cylindrical tanks, volume equals π times the radius squared times the height (V = πr²h); for rectangular cisterns and aquariums, volume is simply Length × Width × Height.
Formula and Calculation Methodology
- r: Internal tank radius in feet (Diameter ÷ 2)
- h: Internal tank height or liquid depth in feet
- 7.48052: Exact conversion factor from 1 cubic foot to US liquid gallons
Once you have the interior volume in cubic feet, multiply by 7.48052 to convert into US liquid gallons (or by 28.3168 for liters). If you are engineering a concrete pad or structural support platform for the tank, remember that fresh water weighs 8.34 pounds per US gallon (62.4 lbs/ft³)—meaning a modest 1,500-gallon vertical water tank exerts over 12,500 pounds of static load.
Standard Vertical Cylindrical Storage Tank Capacities
| Tank Diameter | Tank Height | Volume (ft³) | Capacity (US Gallons) | Full Water Weight (lbs) |
|---|---|---|---|---|
| 4 ft | 5 ft | 62.8 ft³ | 470 gal | 3,920 lbs |
| 5 ft | 6 ft | 117.8 ft³ | 881 gal | 7,350 lbs |
| 6 ft | 8 ft | 226.2 ft³ | 1,692 gal | 14,110 lbs |
| 8 ft | 10 ft | 502.7 ft³ | 3,760 gal | 31,360 lbs |
| 10 ft | 12 ft | 942.5 ft³ | 7,050 gal | 58,800 lbs |
Frequently Asked Questions
How many gallons are in 1 cubic foot of tank volume?
There are exactly 7.48052 US liquid gallons (or 6.2288 Imperial gallons) in 1 cubic foot of space.
How do I convert cubic inches of a small tank into gallons?
Divide the volume in cubic inches by 231, because 1 US liquid gallon is defined as exactly 231 cubic inches.
Why is my tank’s nominal capacity higher than its safe fill volume?
Most industrial and rainwater tanks require 5% to 10% freeboard space at the top to accommodate thermal expansion, inlet plumbing fittings, and overflow vents.