Tank Volume Calculator

Calculate the capacity of a cylindrical or rectangular tank, and how many gallons are in it at a given liquid level.

Leave 0 for the full capacity. For cylinders, enter the height of the liquid.

Liquid volume

564 gal

  • Full capacity564 gal
  • Liters2,135 L
  • Percent full100 %

Estimates only. Round up when you order, and confirm structural details with your local building code.

How to use it

  1. Pick the tank shape.
  2. Enter the dimensions.
  3. Optionally enter the liquid level to get a partial volume.

The formula

Cylinder = π × r² × length

Horizontal partial fill uses the circular segment area: r² × acos((r − h) ÷ r) − (r − h) × √(2rh − h²)

Worked example

Tank shapeVertical cylinder
Diameter4 ft
Length / height6 ft
Liquid level0 ft

Result

Liquid volume564 gal
Full capacity564 gal
Liters2,135 L
Percent full100 %

Tips before you order

  • Use inside dimensions — wall thickness matters on small tanks.

Questions

How many gallons in a 4 ft × 6 ft cylindrical tank?

About 564 gallons.