No method for finding saddle height is perfect. There are many variables involved in bike fit. But I've found this saddle height method to be the most accurate.
After setting your saddle height with this method, you still may adjust it up or down slightly to what feels best. Remember, if you're getting knee pain on the back or side of the knee, your saddle may be too high. If you're getting pain on the front of the knee, your saddle may be too low.
Here's a link to the very quick heel method that I mentioned in the video:
https://www.youtube.com/watch?v=sLuHmiV9khc
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