Tank Volume Calculator
The capacity of a tank — vertical or horizontal cylinder, or rectangular — with the partial volume at a given fill level.
How much a tank holds, full or part-full.
How the tank volume calculator works
A vertical cylinder and a rectangular tank are simple products. A *horizontal* cylinder part-full is not: the wetted cross-section is a circular segment, and its area needs the arccos form — which is why dipstick charts exist.
This calculator handles all three, including the partial fill, so a dip reading converts straight to liters.
Formula: segment area = r² cos⁻¹((r−h)/r) − (r−h)√(2rh−h²)
Worked examples
| Inputs | Full capacity | Note |
|---|---|---|
| A 1.8 m vertical tank, 2 m tall | 5,089 L | 5,089 L full, half at 1 m |
| Horizontal, half full | 5,089 L | exactly 50% at the centreline |
| A rectangular tank | 3,000 L | 3,000 L full |
FAQFrequently asked questions
Why is a horizontal tank so much harder?
Because the wetted cross-section is a circular segment, not a rectangle. The volume is not proportional to the dip reading, which is why dipstick charts are non-linear.
Is a horizontal tank half full at the halfway mark?
Yes, exactly — by symmetry. But at a quarter of the diameter it holds only about 19%, not 25%.
How many liters per centimeter?
Constant for a vertical or rectangular tank; for a horizontal one it peaks at the centreline and falls to zero at top and bottom.
Does this account for dished ends?
No. A tank with dished or hemispherical ends holds a few per cent more than the cylindrical calculation.
How much does a full tank weigh?
A tonne per cubic meter for water. A 5,000 liter tank is 5 tonnes, which is a serious foundation question.
Where these figures come from
- The Engineering ToolBox — material densities, coverage and unit data — bulk densities, concrete at 2,400 kg/m³, board and sheet sizes
- Gypsum Association — gypsum board sizes — 4 × 8 and 4 × 12 ft sheets
- ADA Standards for Accessible Design — ramps (§405) — maximum running slope 1:12
- International Code Council — the International Residential Code
Last checked: September 2026. Coverage rates and material sizes are typical manufacturer figures — check the product you buy.