What is ullage?
Ullage is the empty space from the top of a tank down to the liquid surface. On tankers and bunker tanks, officers measure ullage with a tape, UTI or radar gauge, then convert that height into volume using the ship’s calibrated tank tables. Ullage is preferred to innage when the tank is nearly full, because the remaining empty space is easier to measure accurately.
How this calculator works
This page is for a simple rectangular tank only. Liquid height = Tank height − Ullage. Volume = Length × Breadth × Liquid height. The result is shown in cubic metres and litres. Real ship tanks are not perfect boxes. They have frames, hopper sides, camber and sounding pipes that are not at the geometric centre. Official cargo and bunker figures must come from the approved tank calibration tables, with list, trim and temperature corrections applied.
Who should use it
Use this for a quick estimate or for training. Chief officers and engineers should never use a rectangular estimate for a commercial cargo figure. Always use the ship’s ullage tables and the correct VCF when issuing a cargo or bunker report.