Tank volume calculator
Full tank volume and the volume held at a given level.
Fill in the fields and the result will appear here automatically.
Works out both the full capacity and how much liquid is in the tank right now. In a vertical tank or a rectangular trough the fill is proportional to the level; in a horizontal tank it is not. There the wetted cross-section is a circular segment, so half the height gives exactly half the volume while a quarter of the height gives noticeably less than a quarter. The difference from a geometric cylinder matters: that one returns the volume of a solid, here the answer is how many litres are inside at this level.
How it works
Formula and logic
Use internal dimensions in m. Vertical cylinder: V = πd²·level/4, full height len. Horizontal cylinder: fill is a circular segment along len; 0 ≤ level ≤ d, with small levels evaluated without nearly equal subtraction. The rectangular mode has a square d×d base and height len. Capsule capacity = πd²len/4 + πd³/6, total height len + d; fill is intentionally estimated linearly as Vfull·level/(len + d), not exact spherical segments. 1 m³ = 1000 L; empty and full tanks are valid.
Example
A vertical tank 1.5 m across and 2 m tall filled to 1.2 m holds 2.12 m³ — that is 2121 litres.
Fields and units
- Tank shape — list option
- Diameter or side — m
- Height or length — m
- Liquid level — m
How to use
- — Pick the shape: in a horizontal tank the level is measured from the bottom of the shell.
- — For a cylinder enter the diameter, for a rectangular tank the base side.
- — Height or length: a vertical tank uses its height, a horizontal one its shell length.
- — Measure the level with a dipstick from the bottom; it cannot exceed the tank itself.
Method and limitations
- Calculation method
- Formula and logic
- Limitation
- Use internal dimensions in m. Capsule capacity = πd²len/4 + πd³/6, total height len + d; fill is intentionally estimated linearly as Vfull·level/(len + d), not exact spherical segments.
FAQ
Why does half the height of a horizontal tank give exactly half the volume?
Because a circle is symmetric about its horizontal axis: the segment up to the middle is half the circle. A quarter of the height, though, gives far less than a quarter — the section down there is narrow.
How is this different from a cylinder calculator?
A geometric cylinder returns the volume of the whole solid. Here there is a fill level and an orientation, and the answer is how much liquid is inside now.
How is a capsule handled?
As a cylinder plus a sphere of the same diameter, with the fill spread over the total height. That is an approximation: the exact segment of a domed end needs the shape of that dome measured.
Is wall thickness accounted for?
No: enter internal dimensions. Reduce outside diameter for both walls, and determine clear internal length or height from every end, bottom and lid that is present. Subtracting one wall thickness is not automatically correct for every shape.