Like… why not just use the biggest bottle from the start? Or go with the smallest one and keep things simple?
It feels like one of those baby product mysteries no one really explains... but most of us are dealing with whether you use BM or formula.
So if you are wondering when to switch bottle sizes or why they even exist, here is the simple answer in case you dont like reading... how I write.. or dont have time to read all of this...
You can switch from a 4 oz to an 8 oz baby bottle whenever you want. There is no official ceremony.
You simply realize that filling a bottle to the very top is no longer an excellent system.
If you have more questions keep scrolling...
What are the smaller bottles for?
4 oz bottles are great for smaller feeds, especially in the early months when the baby may only drink 1-3 ounces at a time.
They are:
- Lighter to hold
- Easier to pack
- Less bulky in a diaper bag
- A good size for pumped milk portions
- Convenient for supplementing after nursing
They also make sense when your baby regularly drinks less than 4 oz at a time.
A 4 oz bottle is basically the compact version. Cute, practical, and eventually a little crowded.
Do You Need Both Bottle Sizes?
Not technically (this answer isn't good for Cubby bottle sales, but it's the truth)
You could use 8 oz bottles from the beginning and simply fill them with smaller amounts.
But having both sizes can be convenient & we ended up using both sizes with Fletch so here's my experience
The 4 oz bottle is nice for:
- Early feeds
- Pumped milk
- Travel
- Smaller top-off bottles (these come later)
The 8 oz bottle is better for:
- Larger feeds
- Formula mixing
- Daycare
- Growing feeding amounts
I think most people end up using both.
Because apparently babies grow. Very inconsiderate for anyone trying to keep a perfectly organized bottle cabinet.
Why is extra room important when mixing formula?
Powdered formula must be prepared according to the manufacturer’s directions. The correct amount of water should generally be measured first, followed by the specified amount of powder.
The bottle needs enough room to combine the ingredients without overflowing or coating the collar in formula.
If a prepared feed is close to a 4 oz bottle’s maximum capacity, using a larger bottle can make mixing easier and less messy.
Do you need to change the nipple when you change bottle sizes?
Not simply because the bottle is larger.
Bottle size and nipple flow are two separate things.
A baby may continue using the same nipple flow after moving from a 4 oz to an 8 oz bottle. Change the nipple flow based on feeding behavior and the manufacturer’s age or developmental guidance, not because the bottle body is taller.
Signs that the flow may be too slow include:
- Frustration during feeding
- Very long feeds
- Nipple collapse
- Falling asleep before finishing despite remaining hungry
- Excessive effort to draw milk
Signs that the flow may be too fast include:
- Coughing
- Choking
- Gulping
- Milk leaking from the mouth
- Pulling away repeatedly
- Difficulty coordinating sucking, swallowing, and breathing
Speak with your pediatrician or feeding specialist when feeding appears difficult or unsafe. Our night nurse, Natalie was KEY with these decisions.
How many bottles of each size should you buy?
Typically babies take smaller bottles more often and then slowly they consolidate to bigger bottles more spread out, which means you may eed more bottles in the beginning.
A practical starter set might include:
- Three or six 4 oz bottles
- Three or six 8 oz bottles
- Appropriate nipple flows for the baby’s current stage & other flow speeds (because by the time you realize your baby needs a faster flow you dont have time to wait for even Amazon Prime)
Starting with both bottle sizes provides flexibility and means your prepared for whatever your baby throws your way.
Tip from experience: When Fletcher started daycare at 6 months old, we ended up buying six more bottles. His bottles had to be sent pre-made each day, and we were rotating through four or five bottles daily, so our original supply suddenly did not go very far.
How Cubby tried to make this part easier for you...
It is helpful to have a little of everything on hand. For example, we ended up using the larger bottles to store breastmilk in the fridge, smaller bottles for snacks, tested a faster flow when we weren't sure if that's what Fletch needed , blablabla. So in true Cubby fashion... We created the Complete Cubby Set because it is what I wish we had when Fletcher was a baby.
The Complete Cubby set is the perfect gift or first purchase.
