Stock up on the essentials
For the first weeks. The plan above caps this size on purpose — newborn is the size babies outgrow fastest.
The workhorse size of the first year — most babies spend months here, which is why the plan loads up on it. You can switch size on the page before ordering.
Water-based, unscented bulk wipes — the quiet line item every stockpile forgets until week two.
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Why the charts you have read disagree with each other
Ask the internet how many diapers to stockpile and the answers spread wildly: one guide says about 2,200 diapers for the first year, another says 3,000; one says 4–5 boxes of Size 1, the next says 2–3. They cannot all be right — because each chart secretly assumes a different baby. A small baby who tracks the 10th percentile spends weeks longer in the early sizes than a 90th-percentile baby who blows through them. Any single chart is wrong for most babies.
This calculator starts from your baby instead: it projects weight month by month along standard growth curves (the same CDC-style percentile curves paediatric charts use), converts the projection into days spent in each size using the weight bands printed on diaper packs, and multiplies by the changes-per-day that parents actually report at each age — about 11 a day for a newborn, settling to about 6.5 by the end of the first year. Then it does the two things no chart can: it uses real box counts for your brand, and it subtracts the boxes you already have from the baby shower.
The three stockpile rules that save money
Go light on Newborn. Most babies wear it for two to four weeks; some skip it entirely. It is the size everyone gifts and the size most often returned. Go heavy on Sizes 2 and 3. Together they cover the longest stretch of the first year, and they are exactly the sizes registries under-ask for. Keep every receipt. Unopened boxes exchange for the next size up at almost every big store — a stockpile is a plan, not a bet, when the boxes can move up a size with your baby.
Percentiles, in plain words
A baby at the 50th percentile is exactly average-sized: half of babies weigh more, half weigh less. The percentile is not a grade — a healthy 15th-percentile baby is simply a smaller baby. What matters for diapers is the pace: higher-percentile babies reach the next size’s weight band sooner, so their stockpile tilts toward the bigger sizes earlier. If your baby is already here, entering their current weight lets the calculator re-anchor the projection to their real growth so far.
Prefer to read first? Our guide walks the same maths for an average baby, size by size: How Many Diapers Do I Need in Each Size?
Frequently asked questions
How many diapers do I need in each size?
For an average (50th percentile) baby over the first year, a typical plan lands near: Newborn ~140 diapers (about 2 big boxes), Size 1 ~540 (about 4 boxes), Size 2 ~580 (about 4 boxes), Size 3 ~1,450 (about 9 boxes) — roughly 2,700 diapers in total. Your baby’s percentile, brand box counts and how long you plan ahead move these numbers a lot, which is exactly what the calculator personalises.
How many newborn diapers should I buy?
Fewer than you think. Most babies outgrow Newborn size in two to four weeks, using roughly 150–300 diapers. Start with one or two boxes, keep receipts, and size up the moment leaks start — unopened boxes exchange easily.
How many diapers does a baby use in the first year?
Most babies use between about 2,200 and 3,000 diapers in their first year — around 10–12 changes a day as a newborn, settling to 6–7 a day by twelve months. The wide range is why charts disagree: it depends on the baby’s size and pace.
What is a diaper stockpile?
A diaper stockpile is a planned reserve of diapers bought or registered for ahead of time, spread across sizes so you always have the next size ready. A good stockpile is weighted toward Sizes 2 and 3, light on Newborn, and built from exchangeable unopened boxes.
Should I register for diapers or buy them?
Register for the plan, in the sizes the plan calls for — guests love a specific ask (‘Size 2, please’) far more than a pile of Newborn boxes. Then buy any gaps yourself during sales, keeping receipts so sizes can be exchanged as your baby’s growth declares itself.