Because each brand sets its own weight ranges, and they don't match, especially in the middle sizes. Pampers Size 2 covers 10–22 lb while Huggies Size 2 is 12–18 lb; Pampers Size 4 is 15–34 lb versus Huggies 22–37 lb. So a 24-lb baby lands in Pampers Size 4 but Huggies Size 3. Preemie, Newborn, and Size 1 line up across both. That's why this tool asks you to pick a brand first and never blends the two charts. Enter your weight and switch the toggle to see how the brands compare.

That's normal: the ranges overlap on purpose, so one weight can list under two sizes. Go by fit, not just the number. Size up if your baby is near the top of the range, the tabs don't reach the middle of the waistband, or you're getting leaks and blowouts. Size down if you see red marks or gaps at the legs and waist. The calculator shows the best-centered size plus any other sizes that also list your weight, so you can see the overlap and choose by how the diaper actually sits.

Newborns go through the most (roughly 8 to 12 a day, about 280 a month), and the count drops as they grow: around 10 a day at 2–4 months, about 9 at 5–8 months, and about 7 by 9–12 months. That adds up to roughly 3,000 diapers in the first year and about 8,000 by the time a child is potty trained, per the AAP. These are averages and vary a lot; breastfed babies in particular often need more changes.

On average, US families spend about $100 a month per baby on diapers (Urban Institute / National Diaper Bank Network). A single diaper runs around $0.22, though the real range is wide (roughly $0.10 to $0.74) depending on brand, size, and where you buy. Two things move the price: bigger sizes cost more each (fewer diapers per box), and bulk boxes plus store brands cost less. The calculator lets you set your own per-diaper price and shows the monthly, first-year, and to-potty-training totals.

Yes. Store brands like Target's Up&Up and Costco's Kirkland Signature meet the same safety and performance standards as the national brands and typically cost noticeably less per diaper. Fit and absorbency vary by brand, so it's worth trying a small pack before committing to a big box. But there's no safety reason to avoid store brands, and they're one of the simplest ways to cut the monthly cost.

No. The calculator runs entirely in your browser and stores nothing on our servers. There's no email box and no sign-up. Your inputs are only reflected in the page's web address so you can bookmark, share, or print your result; clear the link and they're gone.