Tank Volume Calculator

Find how many gallons or liters a tank holds, and how much is in it now from the liquid level.

Tank Shape
Units
Measured straight up from the bottom inside the tank.
Fractions and decimals both work. Enter inside dimensions.
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Gallons
Full capacity
Percent full
Liters
Cubic feet
Water weight
Room left
Contents

Tank List

Items you add are saved in this browser.

TankSizeCapacity (Gal.)Contents (Gal.)LitersRemove

How to Calculate Tank Volume

Work out the volume in cubic inches or cubic feet, then convert: 231 cubic inches make one US gallon, so a cubic foot holds 7.4805 gallons. A liter is 1,000 cm³.

Vertical cylinder: π × r² × height   Rectangle: length × width × height
Horizontal cylinder, filled to h: length × [r² × acos((r − h) ÷ r) − (r − h) × √(2rh − h²)]
Capsule: cylinder part + sphere of the same diameter (4⁄3 × π × r³)

For a horizontal tank, the liquid level doesn't track the volume evenly: the tank is half full at half the diameter, but a level of one quarter of the diameter holds only about 20% of the tank.

Worked Example

Horizontal Tank Fill Chart

Level (% of Diameter)Volume (% of Tank)

Tips

Measure inside dimensions. Steel and plastic walls take up space, and many tanks have domed or dished ends that hold more than a flat-ended cylinder. Fuel tanks usually come with the maker's own dip chart; use it when you have it. Water weighs about 8.34 lb per gallon; diesel about 7.1.