Tank Strapping Chart Calculator
Pick your tank's shape, enter its dimensions, and generate a full depth-to-volume chart you can read a dipstick or gauge against — download it as CSV.
Worked examples
Farm diesel tank read off a dipstick
An operator strapping a flat-headed horizontal diesel tank so any driver can convert a stick reading to litres without guessing.
- D
- 2 m
- L
- 5 m
- step
- 0.2 m
A 0.4 m dip = 2,236 L, but 1.0 m = 7,854 L — the middle fills far faster
Upright water cistern with a wall gauge
A flat-bottomed vertical tank where volume rises evenly, so the chart is a straight line the gauge reads directly.
- D
- 2 m
- H
- 3 m
- step
- 0.5 m
Every 0.5 m adds a steady 1,571 L, up to 9,425 L full
How a strapping chart is calculated
A strapping chart is just the tank's volume-vs-depth curve sampled at a fixed step. For each row the calculator takes the dip depth h and computes the liquid volume at that level using the same closed-form geometry a single-answer tank volume calculator uses — there's no lookup table or approximation. The only difference is that here it's evaluated once per increment, from empty to full, to build the whole table at once.
For a horizontal cylindrical shell the wetted cross-section at depth h is a circular segment, so the volume is that segment's area times the shell length L:
Dished, hemispherical, and custom heads add a capped-ellipsoid term on top of the straight section; an oval cross-section stretches the segment into an ellipse; and a vertical cone/frustum integrates a linearly tapering radius up to h. Because the horizontal-cylinder term is strongly non-linear — flat near the bottom and top, steep through the middle — the resulting chart is a curve, which is exactly why reading a dipstick against a proper table beats assuming volume is proportional to depth.
Frequently asked questions
What is a tank strapping chart, and why is it not just a straight line?
A strapping chart (also called a tank chart, dip chart, or gauge table) lists the liquid volume in a tank at each dip depth, so anyone reading a dipstick or sight gauge can convert a height straight to gallons or litres. For a vertical flat-bottomed tank the chart really is a straight line — volume rises evenly with depth. But a horizontal cylinder fills fastest through the middle and slowest near the very bottom and top, because each inch of depth exposes a wider or narrower circular slice. That curvature is exactly why a printed chart exists: you can't eyeball the numbers, so the tank is 'strapped' once and the table is trusted from then on.
How was the original chart on my tank measured — and can this replace it?
Traditionally a tank was strapped by physically measuring its circumference and dimensions with a strapping tape (hence the name) and computing volume per increment. This calculator reproduces the same result from the tank's stated dimensions using exact geometry, which is ideal for a new tank, a lost chart, or a quick cross-check. For custody-transfer or legal-for-trade metering, a certified field strapping is still the official record — treat this chart as an accurate working reference rather than a calibrated certificate.
Which increment should I choose for the depth column?
Match it to how finely you actually read the tank. A dipstick marked in inches wants a 1-inch increment; a wall gauge you read to the centimetre wants a 1-cm (or a round 25/50-mm) step. Finer increments give a longer, more precise table but more rows to scan, so most field charts settle on 1 in, 1 cm, or 2 cm. You can regenerate the chart at a different increment any time without re-entering the tank.
Why doesn't the volume at the halfway depth equal half the tank?
On a horizontal cylinder it does, by symmetry — the halfway depth is exactly 50%. But add dished or hemispherical heads, an oval cross-section, or a cone bottom and the symmetry breaks: a cone-bottom tank, for instance, holds very little near its narrow base, so its halfway depth sits well under 50% of capacity. The chart accounts for every one of these shapes directly, which is the whole reason a per-depth table beats a single 'percent full' rule of thumb.
Can I use this chart for fuel, heating oil, water, or chemical tanks?
Yes — the chart is pure geometry, so it applies to any liquid: diesel and gasoline farm tanks, home heating-oil tanks, water and rainwater cisterns, and process or chemical storage. It reports the physical volume at each depth; it does not apply a temperature correction for fuels (volume-correction factors for gasoline or diesel are a separate step your metering standard may require), so for temperature-sensitive custody metering, apply your VCF to these figures afterward.
Where should I measure the dip depth from?
Always from the lowest interior point the liquid can reach, straight up to the surface. For a horizontal tank that's the very bottom of the round shell, not the top of the saddles or legs it rests on; for a cone-bottom or sphere-bottom vertical tank it's the tip of the cone or the bottom of the sphere. The chart's 0 row corresponds to that lowest point, so line your dipstick's zero up with the same spot.