Well, technically speaking, there is no "correct" length for the stirrups on a western saddle. The western saddle was built for comfort. There are many different suggested ways to check the length, but you must find the length that you feel most comfortable in. Now, you don't want your legs perfectly straight or knees bent like jockeys, but having your legs slightly bent so that you won't go flying off your horse if he bucks should be just about right.
Red Money Maker (Red) - 2004 Sorrel QH Gelding