The way a nappy sits on the child can be an indicator of going up a size. Another indicator could be if there are accidents that are missed by the nappy for not having a big enough size.

Gosh I really cant remember. I think I just noticed that they were not fitting right any more so tried going up a size.

I’ve always looked at the fit and the weight

i go based on weight and then if it’s sung around the waist and legs

I change my son when they’re not fitting around his bum/not holding as much as normal, and if he leaks

I too believe that you should determine it by the weight of your bub.

Just look to the weight of your baby. Every pack of nappies gives a weight indication. I always have the nappies a bit bigger then their weight would indicate as it absorbs a bit better.

When it is harder to get the sticky tabs to sit evenly on the front, and if you have to stetch it as tight as it can go to do up.
Basically if you think they may need to do up then they do.

I have had this problem before, but I just buy the next size up when my baby is within 1 or 2 kg of the next size weight range. If they’re too big, I just keep them for when I need them (which usually is within a few weeks).

Basically the nappy wont fit the size of your childs bottom . Normally I would know by the last few nappys so change to the bigger size before you find out as it is a waste to open a new bag and then realise it won’t fit then .

I found it depends on the brand of nappy. Some nappies are shorter and wider then others.

For shorter nappies when i couldnt cover her bottom properly i went up a size otherwise you risk overflowing nappies. Brands like babylove are like this.

For longer nappies i found they are generally a little less wide and went up in size when they became too little in width. Huggies are like this.

You could also need to go up a size if they wet through the size too fast.

I always upgraded naopies when they seemed too tight or started leaking through.

Persistent leaks, red marks on baby’s skin, or gaps are signs of an improper fit. If your baby is nearing the top of the weight range, it may be time to consider moving up a size.

Use the weight guides on the pack as an indication but I usually found my kids were ready to go up a size when the nappy started leaking or the tabs on the nappy were getting a bit tight to fasten.

When they are getting tight to do up, and get full very quickly (may even leak at night).