5 oz vs 8 oz Bottles? Which One for Your Baby?

Balint Horvath, PhD

Writer, parent, and veteran of baby feeding battles.


Your baby has reached their two-months-old milestone and you’re wondering what size bottle to switch to. Should you transition to the 5 oz bottle now or go for a bigger size? When comparing 5 oz vs 8 oz bottles, which one do you need for your baby?

The 5 oz bottle is good for two to four months old babies. The 8 oz size is used for infants older than six months. However, switching to the 8 oz size is sufficient for babies from two months old. Using the right quantity of milk is essential to avoid under-or overfeeding. 

Key takeaways

  • Knowing the difference between a 5 oz and 8 oz bottle helps you decide if you need both sizes.
  • It’s not recommended to use bigger bottles for newborn babies.
  • All teat sizes fit the 5 oz and 8 oz bottles.
  • Comotomo and NUK bottles are available in 5-ounce and 8-ounce sizes.

The difference between 5 oz and 8 oz baby bottles

Feature5-ounce bottle8-ounce bottle
Size (ml)150ml240 ml
Age2 – 4 months6 + months
Feeding quantity4 – 5 ozs/feed7 – 8 ozs/feed
Feeding times6 – 12 times/day6 – 8 times/day

Do you need both a 5 oz and 8 oz baby bottle?

Bottlefeeding experts recommend switching to the 5-ounce bottle when your baby reaches eight weeks old. At six months, you can transition to the 8-ounce bottle. Many parents find they don’t need both sizes, choosing to switch to either 6 oz or 8 oz bottles from two to four months.

What is a 5 oz baby bottle used for?

The 5 oz bottle is perfect for babies between two to four months old who are drinking 4 to 5 ounces of infant formula or breastmilk at each feed. 

What is an 8 oz baby bottle used for?

The 8 oz baby bottle is normally used for older babies consuming 6 to 8 ounces of milk at every feed. 

Can you use a 5 oz and an 8 oz bottle for newborn babies?

It’s not recommended to use a 5 oz and an 8 oz bottle for newborn babies as they only need very small quantities of milk during this stage. The risks of using a bigger bottle include:

  • Too much air ingestion could result in gas build-up, colic, and infant reflux.
  • Overfeeding

How long to use 5 oz baby bottles for feeding

How long babies use 2 to 8-ounce bottles depends on several factors. The 5 oz baby bottle is normally used for two months. 

How long to use 8 oz baby bottles for feeding?

How long you use an 8 oz bottle depends on how long you’re bottle-feeding your little one. Child experts recommend weaning your baby off the bottle by the time they reach 12 months

How many 5 oz bottles should you get?

A two to four months old baby has up to 12 feeds during a 24-hour period. Four to six bottles should be sufficient. 

How many 8 oz bottles should you get?

A six to eight months old baby feeds up to 8 times a day. Three to four 8 oz bottles are normally enough.  However, if you’re packing for daycare, consider having a few spare bottles just in case. 

Are the teat sizes the same for 5 oz and 8 oz bottles?

Teat sizes are the same for both 5 oz and 8 oz bottles giving you the option of picking the right flow rate for your baby’s feeding pace and style. Keep in mind that not all nipples are interchangeable if you’re using different bottle brands. Teat sizes also vary between wide-and narrow-neck bottles.  

Reasons why you’d want two different-sized baby bottles

So you have a bigger bottle as they grow

The older your baby is the more breastmilk or infant formula they need. Switching to a bigger bottle accommodates your little one’s changing needs. 

To feed your baby the right amount of formula 

Using the right-sized bottle makes it easier to give your baby the right amount of formula. Baby bottles come with measurements marked on the side to help get the right quantities for your baby’s nutritional needs.

To prevent under or over-feeding your baby 

Having the right-sized bottle prevents you from under or overfeeding your baby. Using a smaller bottle runs the risk of not giving your baby enough formula or breast milk per feed. Oh the other hand, you could end up overfeeding your little one if you use a bigger bottle.

Bottle brands that sell 5 oz and 8 oz baby bottles


The breast-like design of the Comotomo baby bottle makes it a popular choice for easy latching and switching between breast and bottle feeding. The Comotomo bottles come in both 5 oz and 8 oz sizes so you don’t need to worry about moving to another bottle brand as your baby gets older.


The NUK baby bottle brand sells both 5 oz and 8 oz sizes. You can choose from the Simply Natural or Smooth Flow Anti-Colic range while the 8 oz bottle is available in glass material.  

Should I get 5 oz or 8 oz bottles?

A 5-ounce bottle is the perfect size for two to four-month-old babies. The 8 oz bottle is adequate for older infants who need more than 7 ounces of milk per feed. However, you can use the 8-ounce bottle for babies from two months old as long as you’re vigilant about measurements. 

Other baby bottle size to compare to each other

Besides these sizes, another very popular option is going for the 4 oz or 8 oz bottles which you might want to look into. Less popular for many but perhaps something relevant for you is considering a 9 vs 11 oz options.

Photo of author


I’m Balint, founder of this site and a father (and dad) to a baby-turned toddler. I found the world of babies so fascinating that I started a blog dedicated only to that topic. By the way, I studied physics, engineering (PhD, MSc), and therefore I do a thorough research when I write about something. Since it’s a blog, of course I also write about my personal experiences.

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