A diaper size calculator helps you choose the best diaper fit by matching your baby's weight and age to brand size ranges. Use it to answer what size diaper your baby likely needs now and compare diaper size charts by weight in one place.
Weight matters most, but age can help when your baby sits in an overlapping range. This chart compares current sizing for Pampers, Huggies, and Luvs so you can pick a better starting fit faster.
Enter both values for a brand-by-brand recommendation.
Best overall starting point
Size 2
FamilyGPT picked this as the most common match across the three brand charts using your baby's current weight and age.
Weight range: 10 - 22 lbs
Typical stage
2-6 months typical
Based on weight and age, Pampers size 2 is the best current fit.
Next size to watch: Size 3 (13 - 26 lbs)
Weight range: 12 - 18 lbs
Typical stage
2-6 months typical
Based on weight and age, Huggies size 2 is the best current fit.
Next size to watch: Size 3 (16 - 28 lbs)
Weight range: 12 - 18 lbs
Typical stage
2-6 months typical
Based on weight and age, Luvs size 2 is the best current fit.
Next size to watch: Size 3 (16 - 28 lbs)
Compare sizes across Pampers, Huggies, and Luvs in one table. Highlighted cells match your current recommendation.
| Size | Pampers | Huggies | Luvs |
|---|---|---|---|
| Preemie | < 6 lbs | < 6 lbs | Not offered |
| Newborn | < 10 lbs | < 10 lbs | < 10 lbs |
| Size 1 | 8 - 14 lbs | 8 - 14 lbs | 8 - 14 lbs |
| Size 2 | 10 - 22 lbs | 12 - 18 lbs | 12 - 18 lbs |
| Size 3 | 13 - 26 lbs | 16 - 28 lbs | 16 - 28 lbs |
| Size 4 | 15 - 34 lbs | 22 - 37 lbs | 22 - 37 lbs |
| Size 5 | 20 - 37 lbs | 27+ lbs | 27+ lbs |
| Size 6 | 23 - 44 lbs | 35+ lbs | 35+ lbs |
| Size 7 | 26 - 50 lbs | 41+ lbs | 41+ lbs |
| Size 8 | 30+ lbs | 46+ lbs | 46+ lbs |
Weight should lead the decision because diaper brands size their products by pounds, not months. Age is still useful as a second check when your baby is between two overlapping sizes.
Many full-term newborns start in Newborn size, which usually fits up to about 10 pounds. Bigger newborns may move into Size 1 quickly because Size 1 often starts around 8 pounds.
Size up when the tabs feel tight, the diaper leaves red marks, the rise looks too short, or leaks and blowouts become more frequent. Babies near the top of a weight range often fit better in the next size.
Overlapping ranges give babies more room to fit different body shapes, absorbency needs, and growth rates. A long, lean baby and a chunky, active baby can weigh the same but fit different sizes comfortably.