Diaper Size Calculator
Enter your baby weight to see the diaper size that fits and when to size up.
| Size | Weight range |
|---|---|
| Newborn | 0 to 10 lb |
| Size 1 | 8 to 14 lb |
| Size 2 | 12 to 18 lb |
| Size 3 | 16 to 28 lb |
| Size 4 | 22 to 37 lb |
| Size 5 | 27 to 35 lb |
| Size 6 | 35 to 60 lb |
Fit matters more than the label
Weight ranges overlap because babies come in different shapes. A baby at 14 pounds might fit Size 1 or Size 2 depending on leg and waist fit. If the tabs close at the middle or leave marks, move up a size even if the scale says otherwise.
Signs it is time to size up
Watch for leaks around the legs, red marks on the thighs and waist, and tabs that no longer reach the center. Frequent blowouts on a baby within the weight range often mean the diaper is too small.
Stocking the right size
Diapers get smaller in count as sizes grow, so a big box of Size 1 lasts through the newborn phase but Size 3 goes fast. Keep one unopened pack of the next size on hand so you are ready when the fit changes.
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Questions about this calculator
What diaper size is 12 pounds?
A 12-pound baby usually fits Size 1 (8 to 14 pounds) or Size 2 (12 to 18 pounds). Check the tabs and leg fit, since ranges overlap.
When should I size up diapers?
Size up when the tabs meet at the middle, you see red marks, or leaks become frequent. Fit matters more than the weight on the box.
How many diapers do I need per day?
Newborns use 8 to 12 diapers a day, and older babies use 6 to 8. A big box of 84 lasts about a week in the newborn phase.
What is the difference between Size 1 and Size 2 diapers?
Size 1 covers about 8 to 14 pounds and Size 2 about 12 to 18 pounds. The overlap lets you switch based on fit rather than weight alone.
Do all brands size the same?
No. Weight ranges are close but not identical, and cut differs by brand. If one brand leaks in a size, try the next size up before switching brands.
What size diaper comes after Newborn?
Size 1 is the next step after Newborn. Most babies move out of Newborn within the first few weeks once they pass about 10 pounds.