How to Determine the Correct Size when ordering boots
The only sure way is to measure both of your feet to determine their size.
Once you know the size of your feet, you can order the correct size boot. Any other technique and you could order the wrong size boot.
What size do you want?
Even if all shoes and boots were made to consistent sizes and you wore a size 10 shoe, you wouldn't always want a size 10 boot.
You might want to wear extra heavy boot socks or multiple pairs of socks in cold weather or for extra cushioning. In that case you'd order the boots a half to full size larger than your foot size and also go up one width.
Remember, you can always adjust the fit of a boot which is too big, but if it is too small, there is no way to make it larger! Boots will not stretch in length, they will stretch a small bit in width. It is better to get boots too large than too small.
How to adjust a boots fit
There are several ways you can adjust the fit.
Change the thickness of the socks worn with the boots.
Two pairs of socks can be used if needed.
Adjust the thickness of the cushioned insole insert.
Adjust the size of the heal insert.
Thinner socks can be worn if the boots are too tight.
Interesting things about your feet: They swell later in the day. As we get older our feet grow a little larger, half to in sometimes a full size. Measure both feet and use the measurement for the larger foot