When it comes to wet diapers the wet diaper should be soaking wet and full of pee when you change it unless you change the diaper before it gets too wet.
Babies 1 year old and under will usually pee a lot and can easily soak a diaper full within 1 to 2 hours.
So if your baby has a soaking wet diaper every 1 to 2 hours then they are usually okay and are hydrated enough.
If your baby has just a damp diaper that is just a little wet every 2 hours then they could be dehydrated.
As a baby gets older they tend to wet less often so when a baby gets to 18 months to 2 years old and older they may go 2 to 3 hours with a dry diaper and then wet the diaper at one time.
So the diaper should be pretty soaked and swelled up if it's a disposable diaper which should happen every 1 to 2 hours.