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Excel .xlsx, no email and no sign-up. Every derived cell is a real formula rather than a number somebody typed.
- Dip chart — 0 to 3,000 mm in 10 mm steps, litres computed by circular segment
- A litres-per-10mm column, because the rise is not linear and that is the point
- Rows past your diameter blank themselves rather than repeating the full tank
The format is argued for in dip to litres, and why it is not linear.
A dip chart is only ever right for one tank
Which is why the ones you can download as a PDF are useless to almost everybody who finds them, and why outlets end up interpolating by eye between two rows of a photocopy made for a tank that was replaced.
Enter the internal diameter and the internal length once, and all three hundred rows compute. Internal, not the shell — a steel tank's wall is several millimetres, and using the outside measurement overstates every figure on the chart.
The column that shows why a chart is needed at all
Litres do not rise linearly with the rod, and the third column makes that visible instead of something you are told. It shows what the next 10 mm is worth, and near the middle of a horizontal tank that is roughly twice what the same 10 mm is worth near the bottom.
A quarter of the diameter holds under a fifth of the volume. Anybody reading a chart as though the two were proportional — or interpolating across a wide gap between rows — is producing a stock figure with an error that changes size depending on how full the tank is, which is the hardest kind to notice.
- The computed full capacity is there to check against the tank's plate. They will not match exactly, because a plate figure is usually the rated capacity and deliberately under the geometric one, but a large gap means a dimension is wrong.
- Rows past your diameter blank themselves, because a chart that keeps printing the same number is one somebody will eventually read the wrong row of.
This is geometry, not a calibration certificate
A tank that is not level, or that has been repaired, will not match its own arithmetic. Use this to work, and settle a dispute with the calibrated chart.