What you need to do is calculate the circumference of your foot at the base of the metatarsal philanges, then divide that by your number of toes, squared.
Then take that remainder and multiply by the number of bites it takes you to eat a ham and cheese omelette.
Once you've calculated this result, create an algorithm which will count the total appearances of the letter 'E' in the movie Doctor Zhivago.
That should give you a good idea of what size boot to order.