Changing diapers for a baby or toddler is usually done every 3 hours but sometimes a toddler may not need a diaper change until 4 hours later.
If the toddler or baby is wearing a good quality absorbent disposable diaper then the toddler or baby may be able to go 4 hours or even 5 hours between diaper changes.
Some toddlers can go 4 hours without the need for a diaper change.
A diaper only needs changed when it gets full of pee or when the diaper has poop in it.
If the diaper has poop the diaper should be changed within 5 to 10 minutes of noticing it.
If the diaper has just a little pee in it then it does not need changed right then and can wait until the diaper is full of pee.
The disposable diapers hold the pee away from the skin so the kid does not feel wet unless the diaper is leaking.
But changing diapers every 3 to 4 hours is a good rule of thumb as that's when most kids need a diaper change.
As a toddler gets older they pee less often so the toddler may go 1 hour to 2 hours after you put the diaper on them and will stay dry for those 2 hours.
My 2 year old son can go 2 hours and keep the diaper dry for those 2 hours and so he's in the diaper dry for those 2 hours and then he pees all at once.
However he can go another hour or so in the diaper and pee again 2 hours later and then I change him into a new diaper.
He sometimes goes 6 hours between diaper changes.
Most times unless he poops my 2 year old son goes through 3 diapers at most per day.