Tank Dip Chart
Calculated at 10% increments of the inside diameter. This geometric table is not a certified tank calibration chart.
| Depth (m) | Liters | US gallons | % full |
|---|---|---|---|
| Enter valid dimensions to generate a chart. | |||
How a Horizontal Tank Volume Calculator Works
The circular end determines the tank's cross-sectional area. Multiplying that area by the inside length gives full capacity. To find liquid volume, the calculator uses only the submerged part of the circle.
Enter the inside diameter, the straight internal length between the flat ends, and the liquid depth. Measure depth vertically from the lowest inside point, not down from the top. If measuring empty space above the liquid, subtract that measurement from the diameter first.
Horizontal Cylinder Volume Formula
Let r be the inside radius, L the inside length and h the liquid depth. The full capacity is:
V = πr²L
How to Calculate Liquid Volume at a Given Depth
The submerged area is a circular segment. Use radians for the inverse cosine:
A = r² arccos((r − h) / r)
− (r − h) √(2rh − h²)
Liquid volume = A × L
The calculator treats empty, half-depth and full conditions explicitly. It uses an equivalent small-angle expansion near empty to avoid loss of precision when subtracting nearly equal numbers.
Worked Example
Consider a flat-ended tank with a 1 m inside diameter, 2 m length and 0.25 m liquid depth. The radius is 0.5 m.
Full capacity = π × 0.5² × 2
= 1.570796 m³ = 1,570.796 liters
At 0.25 m depth, the segment area is approximately 0.153546 m². Multiplying by 2 m gives 307.092 liters, about 81.125 US gallons or 19.55% of capacity. At 0.5 m depth, it holds 785.398 liters, exactly half of its geometric capacity.
Why Depth and Volume Are Not Proportional
The cross-section is narrow near the bottom and widest in the middle. A small rise near the center adds more liquid than the same rise near the bottom. Exactly half the diameter gives half the volume, but most other depth fractions do not match their volume fractions.
This differs from a rectangular tank, where each equal increase in depth adds the same volume. For upright cylinders and other supported shapes, use the general tank volume calculator.
Common Measurement Mistakes
Enter diameter, not radius, and use internal dimensions. This tool assumes a level, uniform cylinder with flat ends. Dished, hemispherical, conical and ellipsoidal ends are not included; using the full outside length of those tanks will produce an incorrect estimate.
A dip chart based on ideal geometry is not a certified calibration chart. Tank tilt, deformation, fittings and sediment can change the relationship between measured depth and actual volume.
Frequently Asked Questions
Is half the depth exactly half the volume?
Yes, for a level, uniform, flat-ended horizontal cylinder. This symmetry does not make the relationship linear at other depths.
What is a tank dip chart?
It pairs liquid depths with calculated volumes for a specific tank. This page provides a table at 10% increments of the diameter and a CSV download.
Can I use this for rounded tank ends?
No. Rounded or dished ends require additional geometry. This calculator supports flat-ended cylinders only.
Methodology & Limitations
Tank Volume Lab calculates ideal geometry in cubic meters, then converts the result using fixed unit definitions. Cylinders use circular area; horizontal partial fills use circular-segment area. Rectangular tanks use base area times height. See the circular-segment formula and NIST unit conversion guidance.
Results are estimates based on ideal internal geometry. Real usable capacity can differ because of wall thickness, tank fittings, baffles, dished ends, freeboard and calibration requirements. These estimates do not replace certified measurement for industrial, safety or financial purposes.