The crackpot index is a method for rating scientific claims or the individuals that make them. The method, proposed (most likely as a joke) by mathematical physicist John Baez in 1998, computes an index by a list of 35 steps, each with a point value ranging from 1 to 50, except for the first step which initializes the computation with a value of -5. Each step may be applied more than once.
Presumably any positive value of the index indicates crankiness.
Though the index was never proposed as a serious method (indeed some of the indicators are either too specific or too vague), it nevertheless has become widely used in settling issues of whether a claim or an individual is a crank.