My LO is so small, I kinda think Size 3 (his current size) will be his last, although I don't plan to potty train until summer when he's 2.5. He's about 22 lbs right now at about 2 years. He wears 12-18 pants, but can still wear most 6 month shorts. I don't know how he will actually fit in clothes without a diaper! (Don't include pull-ups...just day-time diapers.)