Tank Volume Calculator

Tank Volume Calculator works out how much a tank holds, and — the part most calculators skip — how much is actually in it at a measured liquid depth. Pick the shape, type the dimensions and the dipstick reading, and read the gallons straight away. It works completely offline and nothing you enter ever leaves your phone.

HOW IT WORKS
The app uses the standard tank geometry:

1. Full capacity. A cylinder holds pi x r^2 x L. A rectangular tank holds L x W x H. Each dished end is half a spheroid and holds (2/3) x pi x r^2 x c, where c is the dish depth: c = r/2 for a standard 2:1 elliptical head (pi x D^3 / 24), c = r for a hemispherical head (pi x D^3 / 12), and nothing at all for a flat plate.

2. Volume at a measured depth. On a vertical or rectangular tank the liquid area is constant, so volume rises straight with depth. On a HORIZONTAL cylinder it does not. The wetted cross-section is a circular segment, and its area is

A = r^2 x acos((r - h) / r) - (r - h) x sqrt(2rh - h^2)

with r the radius and h the depth from the bottom of the shell. Multiply by the shell length for the straight part, then add the wetted portion of each dished end, k x pi x h^2 x (3r - h) / 6.

3. Because that segment area grows slowly at the bottom, is widest at the centreline and flattens off again at the top, a horizontal tank's dipstick is deeply non-linear. Half the depth is exactly half the volume, but a quarter of the depth is only about a fifth of the contents. Reading a delivery off a bare stick is how tanks get overfilled.

WHAT YOU CAN DO
- Choose a vertical cylinder, a horizontal cylinder or a rectangular tank
- Add flat, hemispherical or 2:1 elliptical dish ends and see what they add
- Enter a measured liquid depth in inches and read the volume instantly
- Build a dipstick / strapping table of 4 to 16 even depth steps — the sheet you tape to the tank
- Compare fill percentage by volume against fill percentage by depth, side by side
- Read every result in US gallons, imperial gallons, litres, cubic feet and cubic metres
- Get the weight of the contents from a specific gravity you set
- See the ullage (the empty space above the liquid) and a 95 percent safe-fill figure
- Open Details for a step-by-step breakdown, and Learn for the geometry in plain language

BUILT FOR CLARITY
A calm tank-yard green design puts the big number first, with the supporting figures right beside it. Light and dark themes, a tiny download, no clutter and no account required.

AN ESTIMATE, NOT A CUSTODY TRANSFER CHART
This is a simplified educational geometry tool. It assumes a level, clean tank with no baffles, coils, heaters, manways or sludge, and dimensions taken inside the shell. Real tanks deform, sit slightly out of level and carry internals, which is why manufacturers issue calibrated strapping charts. Never fill a tank to 100 percent — liquids expand as they warm and a sealed tank filled solid can rupture or vent product, so leave an ullage allowance of roughly 5 to 10 percent. For custody transfer, tax, or any safety-critical measurement, use the manufacturer's calibrated chart or a certified tank gauge and follow your site's fill procedure. This app is for general information and education only and is not professional engineering advice.

PRIVACY
The app collects no personal data and works fully offline. Ads are served by Google AdMob, which may use an advertising identifier as described in Google's policies.

Download Tank Volume Calculator and stop guessing what that dipstick reading is worth.