If you’re a new parent or soon will be, you may be wondering how many diapers to stock up on and which kind to buy.

Some experts estimate that babies go through as many as 2,000 to 3,000 diapers in their first year of life! However, assuming that you’ve opted for disposable, rather than washable cloth diapers, figuring out how many of each size and type to buy can leave even experienced parents scratching their heads.

That’s why we’ve come up with a guide to help you estimate how many diapers in each size to purchase (or add to your registry) before your baby arrives and the best diapers to buy for every stage of development.

Newborn diapers fit babies from about 7 pounds up to 10 pounds, so, unless your child was born prematurely (P-size diapers can also be easily found) or especially large at birth, these will be the size of diaper you’ll likely want to have on hand when you bring your child home for the first time. The best diapers for newborns also offer a cut-out for the umbilical cord area to prevent any rubbing and irritation in that sensitive spot.

How many you’ll need of this diaper size largely depends on how much your child weighs when they are born. Although the average full-term baby weighs about 7 1/2 pounds at birth, your own baby could be smaller or larger than the norm, depending on a wide range of factors that affect birth weight. Still, as a general rule, most newborns gain about 2 pounds in the first month of life.

So, if your child is an average weight at birth and goes through about eight to 12 diapers a day, that would mean you’ll need around 240 to 360 newborn diapers total. Keep in mind that if your child weighs more than 7 1/2 pounds at birth, you’ll need fewer diapers or if they are born smaller than average, you may need even more. 

While some babies may only spend a short time in newborn diapers, most babies will spend at least several months in size-1 diapers since these fit weights between 8 to 14 pounds. So, if you want to buy in bulk or put diapers on your registry to pair with a diaper bag, size-1 diapers are a great choice for this reason.

While the newborn stage is a time of rapid growth, most babies tend to slow down their weight gain after the first month, averaging about 5 to 7 ounces per week. So, as a rule of thumb, 650 to 1,000 diapers will cover about three months at this stage.  If you haven’t already bought one, a great diaper bag — or diaper backpack — will definitely come in handy by this point.

Once your baby reaches 12 to 18 pounds, they can transition to diapers that are size 2. One of the pluses of reaching this stage is that your child will hopefully require fewer diaper changes as they begin to take in more milk or formula at each meal.  This may mean that you only need eight or nine daily diaper changes instead of needing up to 12 each day as before.

Assuming your baby will spend three months at this size, 650 to 750 diapers is a rough estimate of how many you might need to get you through.

By the time your child is ready for size-3 diapers, they will weigh between 16 and 28 pounds. As a rule of thumb, babies reportedly tend to stay in size 3 for the longest period of time  — about six months by some estimates.  Assuming six or seven diaper changes per day, this could mean you might need anywhere between 1,000 to 12,000 size-3 diapers before moving on.

Also, once your child begins sleeping through the night (typically around six months of age), you may also want to consider adding overnight diapers to your stash. These are thicker and more absorbent diapers that help to keep a baby dry for longer stretches of time and prevent leaks and blow-outs that may otherwise wake your child up.

As your child gets closer to the age of 2, you may begin contemplating potty training or your now-toddler may be ready for training diapers that allow them more independence. Alternatively, your child may not be ready for all that freedom yet and may need to transition to size-4 diapers once they’ve grown to the range between 22 and 37 pounds. Since each child’s needs can be unique, you may want to wait before stocking up on this size of diaper until your child is closer to this stage and you have a better sense of what their diapering needs are.

Once you’ve decided they are ready for training diapers, like Pull-Ups or Easy Ups, you’ll find that the sizes are easier to understand. At this stage, the sizes come in a range that aligns with the ones you’d buy their pants in, so 2T-3T or 4T-5T, for example. These diapers are often sold in smaller quantities than regular diapers but hopefully you will begin to only need them overnight, rather than all day.

Finally, if you’re taking your little one to the pool and don’t want them simply peeing in the water as they swim, grab a pack of swim diapers, which don’t swell up and get heavy like regular diapers. You can get disposable or reusable ones in various patterns. Sizing patterns of swim diapers can range by brand but typically align with the numbered sizes that match your baby’s regular size.

However, Pampers uses lettered sizing for its Splashers line of swim diapers, wherein S covers 13-24 pounds, M covers 20-33 pounds and L covers 31 pounds and heavier.

Want more ideas for what to buy before your baby’s arrival? Take a look at our recommendations for the best baby bottles and the best registry gifts.

Margeaux Baulch Klein is a freelance writer and digital strategist based in Los Angeles. She has written for publications like the Huffington Post, New York Daily News, Bustle, and HelloGiggles, among others. Learn More.

The Best Ski Goggles For Women

The Best Plastic Bag Holder

The Best CPAP Machine Accessories