Horizontal Tank Volume Calculator
In a tank on its side, depth and volume are not proportional. The cross-section is a circular segment — wide in the middle, narrow top and bottom — so only the halfway mark is exactly half full. Work out the segment area and multiply by the barrel length.
Your numbers
Litres
396.34L
Fill share
25.2%
Water weight
396.3kg
Formula
Litres = (Radius² × acos((Radius − Fill height) ÷ Radius) − (Radius − Fill height) × √(2RadiusFill height − Fill height²)) × Body length ÷ 1000
Enter the depth read off a dipstick. Below halfway there is far less left than the level suggests.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Diameter (cm)The longest line across a circle — twice the radius. | 100 | 0 and up |
| Body length (cm)The straight section, excluding the rounded ends. | 200 | 0 and up |
| Fill height (cm)How deep the sphere is filled, measured from the bottom. | 30 | 0 and up |
Step by step
Quick reference table
Results when only Diameter (cm) changes and everything else stays put.
| Diameter (cm) | Litres (L) | Fill share (%) | Water weight (kg) |
|---|---|---|---|
| 50 | 246.01 | 62.6 | 246 |
| 75 | 330.04 | 37.4 | 330 |
| 100 | 396.34 | 25.2 | 396.3 |
| 150 | 503.21 | 14.2 | 503.2 |
| 200 | 591 | 9.4 | 591 |
What each result means
| Result | At default values |
|---|---|
| Litres (L)Capacity in litres; one litre is 1,000 cm³. | 396.34 |
| Fill share (%)The filled share of the total volume. | 25.2 |
| Water weight (kg)The weight of the water inside; a litre weighs a kilogram. | 396.3 |
Common mistakes
Enter the depth read off a dipstick. Below halfway there is far less left than the level suggests.
Glossary
- Diameter
- The longest line across a circle — twice the radius.
- Body length
- The straight section, excluding the rounded ends.
- Fill height
- How deep the sphere is filled, measured from the bottom.
- Litres
- Capacity in litres; one litre is 1,000 cm³.
- Fill share
- The filled share of the total volume.
- Water weight
- The weight of the water inside; a litre weighs a kilogram.
Frequently asked questions
Q. How is Horizontal Tank Volume Calculator calculated?
Litres = (Radius² × acos((Radius − Fill height) ÷ Radius) − (Radius − Fill height) × √(2RadiusFill height − Fill height²)) × Body length ÷ 1000 — In a tank on its side, depth and volume are not proportional. The cross-section is a circular segment — wide in the middle, narrow top and bottom — so only the halfway mark is exactly half full. Work out the segment area and multiply by the barrel length.
Q. Can you walk through an example?
With Diameter 100cm, Body length 200cm, Fill height 30cm, the answer is Litres 396.34L.
Q. What do I need to enter?
Enter Diameter, Body length, Fill height. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Diameter (cm) moves the answer to Diameter (cm) 50 → Litres (L) 246.01 and Diameter (cm) 200 → Litres (L) 591. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Enter the depth read off a dipstick. Below halfway there is far less left than the level suggests.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.