How Many Milk Storage Bags Do You Need? FULL Calculation!

woman carrying baby

Milk storage bags are very useful for a number of reasons when switching between breastfeeding and bottle feeding your baby. But, if you’re wondering about how many milk storage bags you need, read on. I’ve done the calculations for you so you don’t need to be wasting money or bags!

The amount of milk storage bags you need depends on how old your baby is, how often you’re pumping and feeding, and if you’re freezing long-term. On average, estimate around 120 to 270 breast storage bags for one month. This equates to around 1,400 to 3,230 bags per year if you’re using disposables.

Do you need breast milk storage bags at all?

If you’re pumping breast milk on a regular basis, storage bags do come in handy. Breast milk bags are the simplest solution to storage, freezing, and serving pumped milk to your baby when you’re not able to breastfeed them. 

Common reasons for using breast milk bags

Building up a freezer stash

Using breast milk storage bags allows you to build up a stash in the freezer while saving space. These bags are designed to be stored flat or upright. Compared to using containers such as bottles, breast milk storage bags are a win-win solution to space saving in the freezer. 

The Medela Breast Milk Storage Bags are great for space-saving in the freezer, the cooler bag, or when keeping in the fridge for 24 hours. 

Good quality bags equals no leaks

Good quality breast milk storage bags prevent leakage. This means you don’t need to stress about milk wastage when defrosting or storing it in the refrigerator. Good quality breast milk bags are made with durable, thick materials which are less likely to burst or tear. 

The Lansinoh Breastmilk Storage Bags have a double zipper seal which prevents messy leaks when storing or defrosting breast milk in the freezer. 

Easy storage for extra milk 

You may end up with more than you expected when pumping and have filled up the bottles for the day. Instead of throwing away this precious food source, stash the oversupply into bags. This means you’ll have an emergency supply for those days when you’re not around to feed your baby. 

The Philips Avent Breast Milk Storage Bags are a good pick for storing extra milk. The wide-neck design makes it easy to transfer milk from the bottle into the bag.  

Convenient for traveling

If you’re traveling with your young baby, it’s way more convenient stashing full breast milk storage bags in the cooler bag. They’re also easier to store in mini-fridges often used in hotel or self-catering rooms. 

Act as a backup

It’s a disaster if a bottle breaks or you’ve forgotten to pack extra bottles in your bag when not at home. Keeping a stash of unused breast milk storage bags in your handbag ensures you’ve always got backup should you need them. They take up very little space and are easy to use when pumping milk. 

Feeding a preemie in hospital

If your preemie is still in hospital, you want to make sure he or she is getting as much breast milk as possible. This can be done by pumping and storing in breast milk storage bags before visiting your little one in the hospital. 

Pump and feed using breast milk bags

Some brands produce breast milk bags that allow you to pump, store, freeze, and feed your baby. The Kiinde Twist Pouch Direct-Pump is one such product. A twist cap, with a thread, lets you seal the bag when full. The bag slips into the natural squeeze bottle and a nipple is added for feeding your baby

Great alternative to bottles

Pumping moms are always asking how to store breast milk hygienically, conveniently, and with minimal mess. This often ends up in a debate between breast milk storage bags versus bottles

Breast milk bags are a great alternative to bottles for storage reasons because of the following features:

  • Space saving: They can be stored flat in the freezer.
  • Hygienic: Good quality bags are pre-sterilized.
  • No leakage: Double zippers and durable material prevents the bag from leaking. 

The art and science of determining how many milk storage bags you need

Being the engineer I am, I’m always using science and mathematics to get the answers I want! The equation of calculating how many breast milk storage bags you need depends are a number of factors such as:

  • How much milk your baby needs per day
  • The size and storage capacity of the breast milk storage bag
  • Storage space available e.g., freezer capacity
  • If you only need for emergencies
  • If you’re traveling with your baby

Let’s take a look at the size and storage capacity of the popular brands I’ve already mentioned in this article.

BrandStorage Capacity
Medela Breast Milk Storage Bags6 oz 
Lansinoh Breastmilk Storage Bags6 oz 
Philips AVENT Breast Milk Storage Bags6 oz
Kiinde Twist Pouch Direct-Pump Direct Feed Breast Milk Storage Bags5 oz (also available in 6 oz and 8 oz sizes)
Haakaa Reusable Breast Milk Storage Bags9 oz

How much milk does a typical baby need per day?

Here’s a table showing the average baby’s intake of breast milk from two weeks to 12 months old. 

AgeQuantity in a single feedNumber of feeds per day
Up to 2 weeks old1-2 oz/feed8 – 10 feeds/day
Newborn (after 2 weeks old)2-3 oz/feed8 – 10 feeds/day
1 to 3 months old4 – 5 oz/feed4 – 6 feeds/day
3 to 6 months old*4 – 8 oz/feed4 – 6 feeds/day
6 to 9 months old*6 – 8 oz/feed6 – 8 feeds /day
9 to 12 months old*7 – 8 oz/feed3 – 4 feeds/day 

*This amount factors in solid foods being added to the baby’s diet.

How much breast milk you should store in each bag

Breast milk storage bags can hold anything up to 5 oz to 9 oz per bag. The average size is 6 oz. 

If you’re using breast milk storage bags to pump the full quota for a day’s feeding, refer to this table for the number of bags you’ll need per day. 

AgeNo. of 6 oz bags/day
Preemie to newborn4 – 10 bags
1 to 3 months4 – 6 bags
3 to 6 months old8 – 9 bags
6 to 9 months old9 – 11 bags
9 to 12 months old5 – 6 bags

Consider where you’ll want to keep your milk bags

The number of bags you need also depends on where you’re going to keep them for emergencies. It’s always handy to have breast milk storage bags stashed for those times when you pump more than what can go into a bottle. Or, you’ve forgotten to pack bottles into your pumping bag.

Based on my figures in the abovementioned table, I would recommend always having 5 to 10 extra breast milk storage bags in the following places:

  • Your car’s cubby
  • At your workplace
  • In your pumping bag
  • At home

Assess how many milk bags you’ll need for long-term storage (in freezer)

If you’re calculating how many milk bags you need for long-term storage in the freezer, you need to factor in:

  • How long you want to keep frozen breast milk
  • The storage capacity of your freezer
  • How much you’re expressing every day into bags

If you’re planning to freeze the extra amount you’re pumping every day you need to estimate the oversupply quantity. If you’re expressing 5 to 6 oz more every day, you’ll need one extra bag every day. 

If you’re planning to stash frozen breast milk for one month, you’ll need 30 extra bags on top of the number you’re using every day. This means you’ll need, in total, 150 to 270 bags per month if you’re averaging four to eight bags per day. 

Estimate how many milk bags you’ll need when traveling

If you’re traveling without your baby, you’ll want to calculate based on how many days you’ll be away from home. This will save you the stress of finding a store selling breast milk storage bags when in a strange environment. 

Use this table to give you a quick overview of bags needed based on days traveling using 5 (6 oz) bags per day, assuming you’re pumping on average 30 oz per day

3 days5 days7 days
15 bags25 bags45 bags

It’s always a good idea to have a few extra bags available in case one breaks or gets dirty. 

Disposable vs reusable milk storage bags

The good news is you can reuse milk storage bags. Disposable milk storage bags can only be used once whereas reusable designs can be used indefinitely. Reusable storage bags such as the Haakaa Milk Storage Bags are made with food-grade silicone, making them long-lasting and hygienic. They can also be used safely in the freezer. 

  • Disposable: You’ll need between 1,400 to  3,240 bags for one year if pumping for 12 months. 
  • Reusable: You can estimate around 40 to 50 reusable storage pouches for one year depending on the quality of the material. 

Watch this video showing how to use Haakaa Milk Storage Bags.

How many breast milk storage bags should I register for?

If you’re wondering if breast milk storage bags expire, you don’t need to stress too much about their lifespan. If they remain unopened, in a cold and dry cupboard, they should last for a long time. 

Disposable milk storage bags can come in boxes of 50 or 100 pieces. If you’re wanting to add them as an item on your baby registry, you could put down two or three boxes of 100 count. This way, you have enough for the first two or three months of pumping. 

How to store breast milk properly in a storage bag 

Use the following steps to store breast milk properly in a storage bag:

  • You can pump directly into the storage bags. 
  • If you’re pumping directly into a bottle, you’ll need to transfer it to the storage bag afterward. Use a food-grade, toxic-free funnel to pour from the bottle into storage bags to prevent spillage.
  • Label the bags with the date and ounces. 
  • When the bag is full (between 5 – 6 oz), seal and put in the freezer, laying down on a flat surface or upright.  

For how many hours can I keep breast milk in a storage bag?

The CDC guidelines recommend the following when storing breast milk. 

Condition of milkCountertop (normal room temperature)RefrigeratorFreezer
Freshly pumped 4 hours4 days6 – 12 months
Thawed from frozen1 – 2 hours1 dayNever refreeze
Leftover after a feedWithin 2 hoursWithin 2 hoursWithin 2 hours


I’ve given you a ballpark figure to help you calculate how many breast milk storage bags you need in one month. I highly recommend using one of the best breast milk coolers on the market for added convenience when using storage bags. This way, you can rest assured your baby’s milk is safely stored for hygienic purposes while not using up your fridge or countertop space.

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