Let's talk size 3 nappies. As your baby grows, understanding when and why to transition to this crucial size is key for comfort and leak protection. This guide will walk you through everything you need to know about size 3 nappies.
Size 3 Nappies: Basic Guide
- Size 3 nappies are generally designed for bubs weighing around 4 to 9 kilograms (that's roughly 9 to 20 pounds).
- This often corresponds to an age range of roughly three to nine months, but weight is the most reliable guide, as all little ones grow at their own pace.
- You might see this size referred to as a 'Medium' in some places.
Nappy Size Conversion Chart (UK/AU Standards)
Aiwibi offers a nappy size chart for new parents:

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When to Graduate to Size 3 Nappies
Here are some signs that your little tacker might be ready for the next size up:
- "Your little one's getting a bit hefty for their current nappies – they're consistently tipping over that top weight limit."
- "Those pesky leaks are becoming a regular thing. No one wants a damp bub!"
- "You're noticing the nappy's leaving little red marks or digging in a bit. That means it's too snug, mate."
- "The nappy just doesn't seem to cover their little bottom properly anymore."
Choosing Size 3: Nappies or Nappy Pants
As your little one grows into Size 3 nappies (6-11kg), usually between 4-9 months old, they hit exciting milestones like rolling, crawling, and even pulling themselves up to stand. This new mobility means their nappies need to keep up—without leaks, discomfort, or restricting movement.
When to Switch from nappies or nappy pants?
- If your baby is crawling/standing – Nappy pants offer better flexibility.
- If nappy changes become a battle – Nappy pants make changes faster.
- If you’re starting potty training prep – Helps babies recognise underwear-like feel.

Common Questions, Sorted!
- "So, how old is a bub usually when they're in size 3s?" (Usually 3-9 months, but focus on weight: 6-11 kg).
- "What's the go with the weight for size 3 nappies again?" (Reinforce the 6-11 kg range).
- "When should we ditch the size 2s for size 3s?" (Refer back to the signs mentioned earlier).
- "Are 'M' size nappies the same as size 3?" (Likely, but always check the weight guidelines on the packaging).
- "What about those nappy pants in a similar size?" (While the weight might be similar, the design and purpose are different for little ones starting to potty train).
Choosing the Right Fit: Happy Baby, Happy You!
- Emphasising the importance of a good fit for both comfort and leak prevention.
- Recommending that parents always check the weight guidelines on the packaging of their chosen nappies.
- Suggesting that if you're unsure, it's always a good idea to try a smaller pack of the next size up to see how they go.
In Conclusion
Finding the Perfect Nappy for Your Little Aussie.
Reassuring parents that finding the right nappy size is all part of the journey. Encourage them to trust their instincts and pay attention to their baby's comfort and any signs of ill-fitting nappies.