# Dip to litres calculator

> A free tank dip chart calculator for 15+ BPCL, IOCL and HPCL underground tank models: dip in cm, mm or cm-and-bars to litres, with water dip, space left and percent full.

Canonical: https://dipdensity.watsinfo.com/tools/dip-to-litres-calculator/
Last updated: 2026-11-02

**Short answer:** Choose the company and the tank model, then type the dip. The litres come from the tank's inside diameter and length, worked out as a horizontal cylinder and checked against the company's printed chart. A BPCL 20 KL tank 210 cm across holds 15,013.36 litres at a dip of 142.5 cm.

The calculator runs in the browser at https://dipdensity.watsinfo.com/tools/dip-to-litres-calculator/.

## The tank models

The calculator knows the same tank models as the app:

- **BPCL:** 8.4, 9, three of 10, two of 15, two of 20, 45 and 70 KL.
- **HPCL:** 9, 16, 22 and 35 KL.
- **IOCL:** 15 and 20 KL, with the deadwood printed on IndianOil's charts.

Each model carries the document it came from, shown under the answer. The models from BPCL's drawings and HP's printed charts match those charts within one to two and a half litres across the whole dip.

## How the litres are worked out

An underground fuel tank is a horizontal cylinder with flat ends. At a dip *h* in a tank of radius *r* and length *L*, the fuel's cross-section is a segment of the circle:

```
area   = r² · acos((r − h) / r) − (r − h) · √(2rh − h²)
litres = area × L ÷ 1000        (cm³ to litres)
```

IndianOil prints a **deadwood** figure on its charts: the volume taken up by fittings inside the tank. It is taken off in proportion. The full working is in [the dip to litres formula](https://dipdensity.watsinfo.com/guides/dip-to-litres-formula/).

## Getting a good dip

A litre figure is only as good as the dip. Lower the rod slowly and straight, let it touch the bottom, and read the cut on the rod at eye level. Take it again if the two readings differ. The [dip reading guide](https://dipdensity.watsinfo.com/guides/how-to-take-a-dip-reading/) has the full routine.

## Questions

### Why does it ask for the model and not just the size?

Two tanks of the same size can have different shapes. BPCL alone has two 20 KL models, one 210 cm across and one 200 cm across. At a dip of 142.5 cm the first holds 15,013 litres and the second 16,086: more than a thousand litres apart. Pick the model whose diameter matches your tank's chart.

### What is the cm.bars option?

Some dip rods mark each centimetre with four bars of 2 mm. A reading written 58.4 then means 58 cm and 4 bars, which is 58.8 cm, not 58.4 cm. Choose cm.bars and type it as you wrote it.

### How is water taken off?

Type the water dip from the water-finding paste. The litres up to the water dip are water; the calculator takes them off the total and shows the fuel alone.

### My tank is not on the list.

Use the tank volume calculator with your tank's inside diameter and length from its chart, or send the chart from the app and we add the model.

## Sources

- [BPCL, Marketing Discipline Guidelines 2024](https://www.bharatpetroleum.in/images/files/MDG-2024-Effective-24-10-2024.pdf)