This is only a vague guide. A ladies size 3 ankle boot (style 1460) will in all likelihood need a different length laces to a men's size 13 ankle boot (style 1460) even though both are an 8-10 eyelet boot.
Some people like to have an extra long lace that wraps around the top of the boot before being tied off. Also the pattern you use to lace the boots can have an enormous difference on the length of the lace required.
We recommend that if you have a whole existing shoe lace then take it out and measure it. If you don't have a complete existing shoe lace then get some thread or a piece of string and thread it through (not forgetting to have sufficient to tie off). When you are happy with the length then cut off the surplus and take it out of the shoe/boot and measure it.
|Pairs of eyelets|
Ankle height boot
High boot (mid calf)
Very high boot (upper calf)