We have a 6 month old little boy. His baby mattress has a side that's firm (for infants) and a side that is soft (for toddlers.) He's about 19 lbs (last time weighed) and I am wondering when should I flip his mattress over.

But more generally, for future reference, when does child stop being an infant and becomes a toddler?


The reason why I asked this is that I want to know the transition period from when a child stops being an infant and becomes a toddler. I figured that a toddler stops being a toddler around 3 - 4 years and my kid is nowhere near there.

  • dictionary.reference.com/browse/toddler - basically when they begin to toddle. I've always felt that the transition from infant to toddler was better associated with the ability to communicate basic needs. For me, it was around 1.5 years when our girls were communicative enough where we no longer had to assume anything
    – Kai Qing
    Commented Feb 12, 2016 at 21:46
  • @LaurentS. That's a good point, I just read the answer that was voted up. It would seem that my question is a duplicate.
    – gp443
    Commented Feb 13, 2016 at 20:52

2 Answers 2


Generally speaking, a child becomes a toddler at around 1 year. This is around the time when they start walking.

About the mattress, keep it on the firm side as long as it isn't impacting their sleep. If you do think it is impacting sleep you might still want to wait to turn it over. The firmer side helps prevent SIDS by keeping it easy both for babies that roll over on their stomach to keep their breathing clear and also for them to roll back over.


There isn't a clear line, but I usually define it around when they start to move by themselves (crawing at first). This is when you need to be extra-careful to baby-proof and avoid hazards.

I'd keep the mattress on "firm" for much longer, that hard surface is great for development. You can read about the dangers of parents who let their child sleep in carseats/swings too much.

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