BABY SHOE SIZES!?

My son is almost 11 months and he has a really big foot. My mom bought him 6-12 mo. size shoes, and they did not even fit. I bought him a size 5 sandal at Old Navy, because that's all they had, and he almost fits it! D: They are a little too big but I think a 3 will be too small. So is 4 a size? And do you guys think that would be a good fit? I need opinions!

01
About Sidney
Current: Brunswick, Georgia
Birth: March 14
On Moms.com since: Jan 30, 2014