How to read it
A Calmar of 1 means the strategy earns in one year roughly what it lost in its worst drawdown. Above 1 over a long window is good; below 0.3 means investors had to sit through a deep loss for modest returns. Because it depends on a single worst episode, Calmar can change sharply when a new drawdown happens.
In Quant Arena
Calmar is computed for every window (1M to Max) from that window's CAGR and maximum drawdown, and it is one of the inputs of the Arena Score. Short windows can produce extreme values, so prefer the 3Y, 5Y or Max windows when comparing.