What a dip reading is
You lower a graduated dip rod into the tank, read the fuel level at the wet mark, and convert that depth to litres using the calibration (dip) chart for that tank. Every tank has its own chart because tanks differ in size and shape. Never use another tank's chart.
How to take a reliable dip
- Dip at the same time every day, ideally before opening and after closing, when no fuel is being delivered or sold.
- Lower the rod slowly to the bottom, hold it still for a few seconds and lift it straight up.
- Read the wet mark at the level of your eyes. Take it twice. If the two readings differ, take a third.
- Convert depth to litres with the tank's own chart and write both figures down.
- Keep the rod clean and straight. A bent or worn rod gives wrong readings.
Book stock and variance
Book stock = opening stock + received - sold
Variance = dip reading - book stock. A negative variance means less fuel than expected.
| Day | Book stock (L) | Dip (L) | Variance (L) |
|---|---|---|---|
| Mon | 19,800 | 19,740 | -60 |
| Tue | 17,200 | 17,150 | -50 |
| Wed | 26,900 | 26,830 | -70 |
| Thu | 24,100 | 24,020 | -80 |
| Fri | 21,500 | 21,445 | -55 |
| Week | -315 |
One day of -60 litres is easy to dismiss. Five days in a row, all negative, is a pattern. At Rs 270 per litre, -315 litres is Rs 85,050 for the week on one tank.
Common causes of stock loss
- Measurement error: the wrong chart, a worn rod, reading at different times
- Unrecorded test litres or own use: fuel drawn out and never written down
- Meter error: a nozzle that dispenses slightly different from what it shows. Ask for the meters to be checked
- Short deliveries: the tanker delivered less than the invoice. Record invoiced and received litres for every purchase
- Evaporation: some loss is natural, especially in heat. Agree a small tolerance and investigate anything beyond it
- Leaks or theft: rare, but a steady unexplained loss on one tank deserves a physical check
A simple daily routine
- Dip every tank at close and record the litres.
- Work out book stock from yesterday's closing, deliveries and today's meter sales.
- Write the variance for each tank.
- If it is outside tolerance, check test litres, nozzle tank assignments and the last delivery first.
- Keep the monthly total. It is the number that matters for profit.
What the loss costs
Use the fuel loss calculator to turn a daily variance into a monthly and yearly rupee figure. Then see how to calculate petrol pump profit.
Doing it automatically
PumpOS calculates book stock from opening stock, purchases and meter sales, takes your dip entry and shows the variance in litres for every tank, every day. Stock is not read from tank gauges. Staff enter dips. See meter readings and dips and purchase shortages.
See variance for each tank, every day
We can show it with sample figures or with your own opening stock.
Frequently asked questions
How do I convert a dip reading to litres?
Use the calibration chart for that tank. It lists litres for each depth. Each tank has its own chart.
How much stock loss is normal at a petrol pump?
Some small loss from evaporation and measurement is normal. The right tolerance depends on your pump, so agree one with your accountant and treat repeated losses beyond it as a signal to investigate.
Why is my dip lower than book stock?
Common reasons are a short delivery, test litres not recorded, a measurement error, or a nozzle assigned to the wrong tank. Check those before suspecting anything else.