What length should they be?
It is above all a question of individual preference. It depends on what is comfortable, and what each person is used to.
However, there is a way of working out the “ ideal ” length. If a person is standing in a relaxed position, with their feet together and their arms by their sides, the top of the knob of the walking stick should be level with their wrist.
Depending on the shape of the knob of the walking stick, for example in the case of a curved handle, it may be easier to turn the walking stick upside down (with the handle on the ground) and then check that the ferrule comes level with the person's wrist.
In general, a man's walking stick would be between 90 and 96 cm, and a woman's would be between 85 and 90 cm.