Tank Capacity Calculator
Enter the inside dimensions of a tank and this works out what it holds, what it holds at any dip depth, and how much surface area there is to coat. It handles ten tank shapes and works in millimetres, centimetres, metres, inches or feet.
It is free to use and there is nothing to sign up for. We built it because we were working these figures out for clients on the phone.
Tank capacity calculator
Enter the inside dimensions and the drawing redraws to scale as you type. Works in metric or imperial, and will tell you the volume at any dip depth as well as the full capacity.
Converting a dip reading into litres is exactly what a calibration chart does. We prepare them from the tank's own measured dimensions.
- — cubic metres
- — imperial gallons
- — US gallons
- — cubic feet
These are gross internal figures worked out from the dimensions you entered, with no allowance for internal fittings. A real tank holds a little less, and is never filled to the very top. Surface area is the shell and the ends, which is what coating is applied to. Final capacity, plate thickness and coating quantity are confirmed on the drawings.
Make a dip chart for this tank depth against litres, ready to print
How to measure a tank
The calculator wants inside dimensions. On a steel tank the difference between inside and outside is only the plate thickness, usually 6 mm, so measuring outside and taking off twice the plate thickness is close enough for planning.
A cylindrical tank
- Diameter. Measure across the widest point of the circular end. If you cannot reach across it, measure the circumference with a tape around the shell and divide by 3.14.
- Length or height. The straight part of the shell, end to end.
- If the ends bulge outwards, the tank has dished or elliptical heads. Measure how far the bulge sticks out past the straight shell and use one of those shapes instead, or the capacity will read low.
A rectangular tank
Length, width and height, measured inside. If it is built into a plant room and you can only reach two sides, measure what you can and send us photographs of the rest.
If you cannot measure it at all
Plenty of tanks have a plate with the capacity stamped on it, or a drawing somewhere in the maintenance file. Failing that, send us photographs with something in frame for scale and we will come and measure it properly. That visit is free and there is no obligation attached to it.
Dip charts, and what this one is not
A dip chart converts a measured depth into litres. Dip the tank, read the depth, look it up, and you know what is in there. The calculator will generate one and lay it out so it prints on a single sheet you can keep in the plant room.
It is worth being straight about what that printed chart is. It is calculated from the dimensions you typed in, for a tank built exactly to those dimensions, with nothing inside it. It is accurate enough to plan a delivery or check a reading against. It is not a calibration certificate, and we would not want anyone using it for anything that money changes hands over.
A chart you can rely on is produced from the finished tank, measured as it actually was built, and that is what we issue with a tank we fabricate or recalibrate. The difference matters most on a horizontal tank, where a small error in diameter changes every reading in the middle of the range.
Why a dip stick misleads people
On a horizontal cylinder, half the depth is half the volume, but a quarter of the depth is only about a fifth of the volume, and three quarters of the depth is about four fifths. The tank fills slowly at the bottom, quickly through the middle and slowly again at the top. Estimating by eye off a dip stick will be out by thousands of litres on a large tank, which is how sites run dry while the gauge says there is plenty.
Set the shape to a horizontal cylinder above, drag the fill slider, and watch the litres against the percentage. That gap is the whole argument for a proper chart.
What we do with these numbers
If the tank you are sizing is one you want built, press the button in the calculator and the figures come through to us with your enquiry, so we are not starting from a blank page.
- New tank fabrication, from the drawing through to delivery and connection
- Inspection, cleaning, blast cleaning and recoating of tanks already in service
- Hydrostatic and pressure testing
- Calibration and calibration charts, prepared from the tank as built
- Digital level monitoring, supplied and installed
Common questions
Is the calculator free to use?
Yes, and there is nothing to sign up for. Use it as often as you like, whether or not you ever ask us to quote.
Can I use the printed dip chart for fuel reconciliation?
For your own day to day checks, yes. Not for anything where money changes hands on the reading, because it is calculated from the dimensions entered rather than measured from the tank. We can prepare a proper chart from the tank itself.
Why is my tank holding less than the calculator says?
Gross volume assumes an empty shell filled to the very top. A real tank has baffles, pipework and a sump taking up room, and is never filled to the brim. A few per cent under the calculated figure is normal.
Which shape should I pick for my tank?
If the ends are flat, a plain cylinder. If they bulge outwards, dished or 2:1 elliptical. If they are fully rounded like the end of a capsule, a capsule. Send us a photograph if you are not sure and we will tell you.
Do you build all of the shapes listed?
No, and the list says which. We fabricate horizontal, vertical and rectangular tanks. The other shapes are in the calculator so you can work out a tank you already have, whoever built it.
Can you work out the coating quantity too?
The calculator gives the surface area but not the paint quantity, because that depends on the coating system, the number of coats and the film thickness. Send us the area and what the tank holds and we will tell you.