Tank Volume Calculator: Gallons in Any Tank Shape
This tank volume calculator finds how much a tank holds and how much liquid is in it right now. Choose a rectangular tank, a vertical cylinder, a horizontal cylinder or a sphere, enter the dimensions in inches, feet or centimeters, and add the liquid depth for a partly full tank. Horizontal tanks use the exact circular-segment formula, so a half-full 48-inch tank reads correctly instead of guessing. Results show US gallons, liters and cubic feet, plus the percent full, for water, fuel oil and rain barrels.
Tank Volume Calculator
Find the total and filled volume of a rectangular, cylindrical or spherical tank in gallons.
How to use the Tank Volume Calculator
- Pick the tank shape.
- Choose inches, feet or centimeters.
- Enter the size and the liquid depth.
- Read total volume, filled volume and percent full.
Tank volume formulas
Rectangle: L × W × H · Cylinder: ฯ r² L · Sphere: 4/3 ฯ r³ · Horizontal fill: L × (r² acos((r−h)/r) − (r−h)√(2rh − h²)) · 1 US gal = 231 in³
Features
- Rectangular, cylinder and sphere
- Exact horizontal tank fill
- US gallons, liters and ft³
- Percent full
Frequently asked questions
How do you calculate the volume of a cylinder tank?
Volume = ฯ × r² × length. A tank 48 inches across and 72 inches long holds ฯ × 24² × 72 = 130,288 cubic inches, or about 564 US gallons.
How many gallons are in a cubic foot?
One cubic foot holds about 7.48 US gallons. One US gallon is 231 cubic inches.
How do I find the volume in a partly full horizontal tank?
The liquid forms a circular segment. Its area is r²·acos((r−h)/r) − (r−h)·√(2rh−h²), times the tank length. The calculator does this for you.
Why is a half-full horizontal tank not the same as half the depth in gallons?
At exactly half depth it is half full, but at other depths the round shape means the volume changes faster near the middle than near the top or bottom.
Does the wall thickness matter?
Yes. Measure the inside dimensions for an accurate capacity. Outside measurements slightly overstate the volume.