Tools · Baby
Diaper Size Calculator
Free diaper size calculator. Enter your baby's weight to find the typical diaper size range and an estimated monthly diaper usage.
Enter your baby's weight to see a typical size range.
Sizing varies by brand — treat this as a starting point and adjust based on fit (no red marks, no leaks, comfortable at the waist and legs).
How Diaper Size Is Estimated
Most disposable diaper brands size primarily by weight, using broadly similar (though not identical) ranges: Newborn up to about 4.5 kg, Size 1 around 3.5–6 kg, Size 2 around 5–8 kg, Size 3 around 6–10 kg, Size 4 around 8–14 kg, Size 5 around 11–18 kg, and Size 6 for roughly 15 kg and up. Because these ranges overlap heavily between adjacent sizes, weight alone is only a starting point — actual fit around the legs and waist matters more day to day.
The monthly usage estimate multiplies a typical daily change count for your baby's age — higher in the newborn period, gradually decreasing — by 30 days, to give a rough sense of how many diapers to have on hand.
Frequently Asked Questions
Why do diaper sizes overlap between weights?
Diaper brands intentionally build in overlap between sizes because babies of the same weight can have very different body shapes — some are longer and leaner, others shorter and rounder. If a diaper is leaking or leaving red marks at the leg or waist despite being the "right" size by weight, sizing up (or down) is completely normal.
Should I switch size the moment my baby crosses a weight threshold?
Not necessarily. Watch for actual fit signs — red marks, leaks, or a diaper that no longer fastens comfortably — rather than switching the day the scale crosses a number. Many babies stay comfortably in one size for weeks past the point where the chart suggests moving up.
How is the monthly usage estimate calculated?
It's based on typical change frequency by age: newborns are changed roughly 10–12 times a day, dropping to about 6–8 times a day by 6 months, and around 5–6 times a day by a year, as babies urinate less frequently but in larger amounts. Multiply the daily estimate by 30 for a rough monthly total.
Do cloth diapers follow the same size chart?
Not exactly — many cloth diaper systems use adjustable snaps that cover a much wider weight range per size (sometimes birth to potty training in one "one-size" product), so check your specific brand's sizing rather than relying on disposable diaper weight ranges.
Weekly parenting tips, no spam
Evidence-based guidance for your child's stage — straight to your inbox.
Track Diaper Changes with Whispie
Log wet and dirty diapers alongside feeding and sleep to spot patterns early.