# Horizontal tank volume calculator

> A free calculator for the litres in any horizontal cylindrical tank with flat ends, from inside diameter, length and dip in cm, with optional deadwood.

Canonical: https://dipdensity.watsinfo.com/tools/tank-volume-calculator/
Last updated: 2026-11-02

**Short answer:** Type the tank's inside diameter and length in cm, and the dip. The litres come from the area of the circle's segment times the length. A tank 200 cm across and 671.8 cm long holds 21,105 litres when full.

The calculator runs in the browser at https://dipdensity.watsinfo.com/tools/tank-volume-calculator/.

## The sum

For a horizontal cylinder of radius *r* and length *L*, filled to a depth *h*:

```
area   = r² · acos((r − h) / r) − (r − h) · √(2rh − h²)
litres = area × L ÷ 1000
```

All lengths are in cm, so the area is in cm² and area × length is in cm³; 1,000 cm³ is one litre.

The calculator also shows **one cm at this dip**: how many litres one centimetre is worth at the level you typed. Near the middle of the tank a centimetre is worth the most; near the bottom and the top it is worth much less. That is why a small mistake in the dip matters most when the tank is half full.

## Questions

### Where do I find my tank's diameter and length?

On the tank's calibration chart or its drawing. Use the inside diameter, not the outside: the steel wall is several millimetres thick.

### What is deadwood?

Pipes, a dip pipe and other fittings inside a tank take up room that holds no fuel. IndianOil prints this figure on its charts; for a 20 KL tank it is 18 litres. Type it if your chart shows it.

### Does it work for tanks with domed ends?

No. It is for flat ends, which is what Indian underground petrol pump tanks use. A tank with dished ends holds more; use its own chart.