Gauge a horizontal tank from a dipstick
A half-full drum is not at half height. Circular-segment math converts dipstick depth into litres — or the depth for a target fill.
Tools used in this guide
The job
A horizontal cylinder fills unevenly: the bottom half of the depth holds less than half the volume because the cross-section is narrow near the floor. A dipstick of 0.5 m in a 2 m tank is only 19.6% full.
Depth → volume, or % → depth
Enter diameter and length, then a measured fill depth to get volume and fill fraction — or enter a target percent to get the depth to gauge to.
Worked example
A flat-headed tank 2 m in diameter and 5 m long holds 15.708 m³. A dipstick reading of 0.5 m means 3.071 m³ — 19.55%, not 25%. To reach exactly 25%, fill to 0.596 m of depth.
Scope
Flat-headed horizontal cylinders, 0.01–100 m per dimension. Dished ends, tilted tanks, and per-tank strapping tables are not modeled — certified gauging needs the tank's own table.