What is angle of loll?
If GM is negative the ship is initially unstable and will not sit upright. It rolls to one side and finds a new equilibrium called the angle of loll. At that angle the righting lever is zero again. Loll is dangerous because a small extra heeling moment can make the ship flop to the other side. It is not the same as a list caused by off-centre weights when GM is still positive.
How this calculator works
For small angles, tan²θ ≈ −2 GM / BM. GM must be negative and BM must be positive. The result is only a first estimate from wall-sided theory. Real ships need the GZ curve from the stability booklet. Correcting loll is done by lowering the centre of gravity — typically by filling double bottoms first — not by putting ballast high up.
Who should use it
Useful for officers studying stability or checking a suspected negative-GM condition. If the ship is lolling at sea, follow the company emergency stability procedure and the Master’s orders immediately.