Adorable on your little at every age and stage! Start off oversized and watch as they grow into it as a more snug fit. Kid tested and kid approved!
For reference: Milo (pictured) wears the 2T and was just over a year- we sized up so it would be extra big and long for layering and will get more snug as he grows.
Size 12 month: great for babies under a year.
Size 2T: great for ages 1-2.5
Size 3T: great for ages 2-3.5
Size 4T: great for ages 4-6