So this is kind of a weird question. I had an all-purpose saddle I was riding in, and I recently sold it. I've got a dressage saddle on the way, and it doesn't come with leathers... I don't have any clue how to determine leather-length. The leathers I rode in before seemed to fit alright... but I didn't even think to measure them. I am 6'2 and very leggy.
While we're on the subject of leathers, I always think it's funny to read a product description that says "Nylon stirrup leathers" lol... they're not leathers then, they're nylons :P