🔼When to Size Up
- Frequent leaks overnight or during naps - the absorbency may no longer be enough for your baby's output. Larger sizes contain more SAP (super absorbent polymer) and offer higher absorbency capacity.
- Blowouts up the back or sides - they may have outgrown the length/depth and need to size up for better coverage.
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Red marks or indentations around the waist or legs - a sign it's too snug.
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Body shape differences - not all babies carry weight the same way. A baby with chubby thighs, rounder tummy or longer torso might outgrow the fit of the nappy size sooner than a baby of the same weight with a different shape.
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Sudden growth spurts - they can come out of nowhere and mean they have outgrown the size almost overnight.
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Nearing the top of the weight range - Even if your baby is technically within the weight range on the pack, the fit might already be too small.
Example: If your baby is 7 kg and you're still using Size 3 (4–8 kg), try moving to Size 4 (7–14 kg) — especially if you're seeing red marks, blowouts, or overnight leaks.
🔽When to Size Down
- Gaps at the waist, back or thighs - the nappy isn't sealing properly. A smaller size will give a snug, secure fit that holds liquid in.
- Nappy bunches, sags or slides down - a loose nappy will bunch at the crotch and slide down when they crawl or walk.
- Tabs overlap too much - if the tabs cross over each other at the front, the nappy is too large.
🩳When to switch to pull-ups
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Baby won’t lie still for nappy changes.
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Leaks happen during crawling, walking for play time.
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You're starting the toilet training journey.
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You need faster, fuss-free changes on the go.
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Leaks happen during crawling, walking or playtime.
So What Size Should You Choose?
Here’s how to make sure you’re choosing the right nappy size every time:
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Follow the weight guidelines on the Joonya pack or the size guide below - they’re a great starting point.
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Size up if your baby is near the top of the weight range or you’re seeing leaks, blowouts, or tight tabs.
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Try overlapping sizes — if your baby is between weights, try the next size up and see which fits best.
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Test before you commit — before buying a bulk box, try a smaller Trial Bundle of Joonya nappies to make sure the fit is perfect for your baby.
⏳ Many parents hesitate to move up a size to avoid wasting nappies, but in reality, sizing up sooner can save you money, time, and laundry in the long run.
Pro Tips for a Leak-Free Nappy Routine
A good fit isn’t the only key to preventing leaks. Keep these tips in mind:
👉 Run a finger around the leg cuffs to make sure they’re untucked and snug.
🎯 Position the nappy correctly — high enough at the back and centered in the front.
⏰ Change regularly — even the best-fitting nappy can leak if it’s too full.
- The Joonya Team 💚