When to Change Diaper Sizes: A Complete Size Chart Guide for 2026
The Ultimate Diaper Size Chart for 2026
Getting the right diaper size is one of the simplest ways to prevent leaks, blowouts, and skin irritation. But with every brand sizing slightly differently, it can be confusing. This guide gives you a clear size-by-weight chart plus the telltale signs that it's time to move up.
Diaper Size Chart by Weight
Preemie: Up to 6 lbs (2.7 kg) — for premature and very small newborns. Newborn (N): Up to 10 lbs (4.5 kg) — most babies wear this for 2-4 weeks. Size 1: 8-14 lbs (3.6-6.4 kg) — typically fits from birth to 4 months. Size 2: 12-18 lbs (5.4-8.2 kg) — usually 3-8 months. Size 3: 16-28 lbs (7.3-12.7 kg) — usually 5-15 months. Size 4: 22-37 lbs (10-16.8 kg) — usually 12-24 months. Size 5: 27+ lbs (12.3+ kg) — usually 18+ months. Size 6: 35+ lbs (15.9+ kg) — for larger toddlers.
5 Signs It's Time to Size Up
Don't rely on weight alone. Watch for these signs: frequent blowouts up the back, red marks on your baby's thighs or waist from elastic, difficulty closing the tabs without stretching, the diaper looks visibly small, and frequent leaks that didn't happen before.
Overlap Sizes Are Normal
You'll notice weight ranges overlap between sizes. This is intentional — babies with chunky thighs might need a larger size earlier, while leaner babies can stay in one size longer. Always prioritise fit over the number on the package.
Night-Time Sizing Tip
Many parents find that sizing up one size for overnight diapers helps prevent leaks. A slightly larger diaper with more absorbent material can handle 10-12 hours without changes. CuddleKin bamboo diapers are designed for extended overnight wear.