4 oz vs 8 oz Bottles? Which One Do You Need for Your Baby?

Balint Horvath, PhD

Writer, parent, and veteran of baby feeding battles.


Bottlefed newborns transition from 2-ounce baby bottles as soon as four weeks and at this stage, you need to decide which size to switch to. Which is better when comparing 4 oz vs 8 oz bottles? Should you go straight for the larger bottle or switch slowly, starting with the 4-ounce size?

Newborns drink small quantities during their first month. When they’re 4 weeks old, they consume more breast milk or formula and can drink from a  4-ounce bottle. From 8 weeks old, your baby can switch to the 5 or 6-oz bottle before moving to the 8-oz size from 4 to 6 months old.

Key takeaways

  • The main difference between the 4 oz and 8 oz bottles is the volume they can hold and the age group they’re most suitable for.
  • Having both 4 oz and 8 oz bottles is useful for babies from eight weeks old and older.
  • It’s not recommended to use 8 oz bottles for a newborn baby. 
  • The 4 oz bottle isn’t always necessary and you can switch to a 5 oz or 6 oz size instead. 
  • All teat sizes fit both 4 oz and 8 oz bottles.
  • Not all popular baby bottle brands sell 4 oz and 8 oz sizes!

The difference between 4 oz and 8 oz baby bottles

Feature4-ounce bottle8-ounce bottle
Size (ml)120 ml240 ml
Age1-month-old2 – 6 months old
Feeding quantity2 – 4 ounces per feed4 – 8 ounces per feed
Feeding times7 – 8 feeds/day6 – 8 feeds/day

Do you need both 4 oz and 8 oz bottles? 

4 oz bottles and what they’re for

The smaller, 4 oz bottle is easier to pack into diaper bags when traveling. This sized bottle can normally hold up to 5.5 ounces of milk so you can still use them for your two to four-month-old baby who is drinking between 4 to 5 ounces per feed

8 oz bottles and what they’re for

The 8-ounce bottle is best for babies drinking between 6 to 8 ounces of breast milk or infant formula per feed. Using bigger bottles saves you from having to refill during a feed when meeting your baby’s nutritional requirements.  

Bottom line

Deciding if you need both 4 oz and 8 oz bottles is an ongoing debate that rages on among many parents! Using the 4-ounce bottle for your one-month-old baby prevents the following:

  • Gas and colic symptoms: Using larger bottles could cause your baby to ingest more air, resulting in gas or colic symptoms
  • Overfeeding: If you’re not careful about measuring the exact quantity for your baby’s growth and development stage, you could end up overfeeding them when using larger bottles. 

Deciding if you need both bottle sizes is a personal choice for both you and your baby. The 4 oz bottle is an easier size for young babies to hold while the bigger 8 oz can be cumbersome for smaller hands. However, the 8oz bottle is the best option once your baby starts drinking more than 4 to 5 ounces per feed. 

Can you use an 8 oz bottle for a newborn baby?

Using an 8 oz bottle for a newborn baby isn’t recommended! For the first four to eight weeks, your newborn baby will only drink 1.5 to 3 ounces of breast milk or infant formula. Using larger bottles runs the risk of overfeeding your newborn when their tums can only handle small quantities at each feed.

If you don’t want to start with 2-ounce bottles, you can go straight to 4-ounce or even 5-ounce sizes for your newborn. Make sure the measurements are clear so you don’t feed your little one more than they need or can handle at this age. 

Are 4 oz bottles necessary? 

The 4 oz bottle is a popular size for many parents bottle-feeding their babies. While it’s not necessarily the only option available for newborns and babies up to four months old, the 4 oz bottle is a convenient size at this stage. It’s ideal for preventing overfeeding and unpleasant gas or colic conditions. 

This video talks about the danger of overfeeding babies.

Are the teat sizes the same for 4 oz and 8 oz bottles? 

Teat sizes for both 4 oz and 8 oz bottles are the same and can be switched according to your baby’s feeding pace. Newborn babies up to the age of three months should start with a slow-flow nipple or Level 1 teat and they’re available for both 4 oz and 8 oz baby bottles. 

By the time your baby is using an 8 oz bottle, you use the Level 3 or 4 teats. However, this depends on whether your baby prefers a slow, medium, or fast-flow nipple. 

How long do babies use a 4-oz bottle?

Babies you typically a 4-oz bottle between the time when they’re 4 weeks old and 2 months old. I wrote about this in another article on how long babies use 2-8 oz bottles.

How long do babies use a 8-oz bottle?

When babies turn 6 months old you can start giving them an 8-oz bottle and you can do for another 6 to 12 months. Here’s an article I wrote about different bottle sizes and how long you should use each of them.

Bottle brands that sell 4 oz and 8 oz bottles 


The Comotomo bottle is designed to resemble the mother’s breast and is constructed with soft silicone for a soothing, gentler touch. It’s not available in the 4-ounce size. 

Comotomo baby bottles come in two sizes – 5 oz and 8 oz. The 5oz bottle comes with a slow-flow or Level 1 nipple ideal for newborns while the 8oz has a medium-flow teat for older babies. Faster flow nipples can be used with either of these bottle sizes. 

Dr. Brown

Dr. Brown offers a range of bottles and they all come with the popular internal venting system ideal for controlling colic, gas, and infant reflux. The baby bottles are available in different shapes and sizes.

Dr. Brown’s standard bottles are available in three sizes namely 2 oz, 4 oz, and 8 oz. The Standard wide-necked bottles are available in 4 oz and 8 oz sizes. The Options wide-necked design is available in the larger 4-ounce and 9-ounce sizes. 


The NUK Simply Natural Bottle range is available in both glass and plastic material. They’re designed to help transition babies from breastfeeding to the bottle. 

NUK bottles are available in 4 oz, 5 oz, 8 oz, and 9 oz sizes and the Simply Natural nipples come in different flow rates with each teat having 9 holes. When comparing Dr. Brown vs NUK bottles check the differences before picking the right brand for your bottle-fed baby. 


There are some crucial differences between 4 oz and 8 oz baby bottles that should be noted before deciding if you need both. Size can make a difference as well as wide-neck vs narrow-neck bottles and other features such as venting systems. You might need to upgrade, for example if your baby is hitting his bottle fervently, so you’ll need to decide soon – which one will it be for your bottle-fed baby?

Later you might want to go for even higher-sized bottles and in that case you might want to read about the differences between a 9 oz and a 11 oz bottle which I wrote about in a separate article. Or if you’re looking into the 8 oz option, then you might one to compare it with a 5 oz option?

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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