Horizontal cylindrical tank fill volume calculator
Measure the liquid depth from the tank bottom and enter the inside diameter and length to see what is left in a water or diesel tank.
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How to use it
- Enter inside diameter, tank length, liquid depth and length unit.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Filled segment area = r² × acos((r − h)/r) − (r − h) × √(2rh − h²); volume = segment area × tank length, where h is the liquid depth.
Example
Inputs: Inside diameter = 200, Tank length = 400, Liquid depth = 50, Length unit = Centimeter (cm). Result: Liquid volume: 2,456.739 L; Total tank capacity: 12,566.371 L; Fill percentage: 19.55%.
Limits and caveats
- Assumes a level horizontal cylinder with flat ends; domed ends add volume this tool does not count.
- Use inside dimensions, since wall thickness reduces the real capacity.
Questions about this tool
Why not just multiply the depth ratio by capacity?
The tank width changes with depth. Half depth does give half the volume, but a quarter depth gives about 19.6% of capacity, not 25%.
How do I measure the liquid depth?
Lower a clean stick straight down through the top opening to the bottom, then measure the wet part.
Does it work for diesel and water tanks?
Yes. The calculation is purely geometric, as long as the tank is horizontal and level.