When measuring your baby's feet for shoes/socks, is there any trick to it? I feel like the number I'm getting is crazy and I can't find instructions anywhere online (maybe it's a stupid question).

Basically I'm trying to buy some socks for my 3mo LO for the fall/winter, so he'll be something like 5 - 10 months old during the cold months. He is on the bigger end, wearing 6mo clothes, but his foot is already measuring 4.5in which puts him almost out of infant sizes already. It's looking like I should order 12-24m socks, but can that be right? Help this FTM, please!