Diapers that don't fit properly are one of the most common — and most overlooked — causes of leaks, blowouts, and diaper rash. The good news? Your baby gives you clear signals when it's time to size up. Here's exactly what to look for.
1. Frequent Leaks (Even After a Fresh Change)
If you're changing a diaper that's barely wet but already leaking, the fit is the problem — not the brand. A properly fitted diaper should contain at least one full wetting without leaking around the legs or waist.
What's happening: The diaper is too small to hold the volume your baby produces, or the leg cuffs can't seal properly around growing thighs.
2. Red Marks on the Skin
Check your baby's waist and thighs after removing a diaper. Light imprints are normal, but deep red marks or indentations that linger for more than a few minutes mean the diaper is too tight.
This is especially common around the leg elastics and waistband when a baby has chunky thighs or a rounder belly.
3. The Tabs Don't Reach the Center
When fastening the diaper, the adhesive tabs should land roughly in the middle of the waistband. If you're stretching them to the far edges — or they barely close — you need the next size up.
Conversely, if the tabs overlap past the center, the diaper may be too big.
4. Blowouts Are Happening Regularly
The occasional blowout is a rite of passage. But if it's happening multiple times a week, the diaper isn't containing your baby's output effectively. This usually means the leg cuffs are too loose or the diaper is too small overall.
Quick check: After putting on the diaper, run your finger around the leg cuffs to make sure they're fully unfolded and snug — not gaping.
5. The Diaper Looks Too Small Visually
Trust your eyes. If the diaper looks stretched, doesn't cover the bottom fully, or rides up the back, it's time to move on. A well-fitting diaper should sit just below the belly button and cover the entire bottom comfortably.
6. Your Baby Seems Uncomfortable
Babies can't tell you the diaper is pinching — but they'll show you. Unusual fussiness during or after diaper changes, or squirming and pulling at the diaper, can be a sign of discomfort from poor fit.
Diaper Size Guide by Weight (General Reference)
| Size | Baby Weight | Typical Age |
|---|---|---|
| Newborn (NB) | Up to 4 kg | 0–4 weeks |
| Size 1 | 3–6 kg | 1–4 months |
| Size 2 | 5–8 kg | 3–8 months |
| Size 3 | 7–11 kg | 6–12 months |
| Size 4 | 9–14 kg | 10–18 months |
| Size 5+ | 12 kg+ | 18 months+ |
Note: Weight ranges overlap between sizes. When in doubt, size up — a slightly bigger diaper is always better than one that's too tight.
When to Size Up vs. Try a Different Brand
If you're between sizes and experiencing leaks, try the next size up first. But if the fit seems right and leaks persist, the issue may be the diaper's absorbency or design — that's when switching brands makes sense.
Different brands cut their diapers differently. Some run narrow in the leg, others are wider at the waist. It often takes a little trial and error to find the right match for your baby's body shape.
The Bottom Line
Don't wait until you've used up an entire pack in the wrong size. As soon as you notice two or more of the signs above, it's time to move up. Your baby will be more comfortable, and you'll have fewer messes to deal with.
Ready to find the right size? Browse our full diaper range — available in economy and jumbo packs so you can stock up once you've found the perfect fit.
