Depending on how much the child wets a 2 year old will usually go through 4 or 5 diapers per day.
As a child gets older they tend to hold the urine in longer and wet on a schedule and you can usually time it when they'll be peeing and needing a diaper change.
As toddlers get older they go through less diapers since they won't have a wet or dirty diaper as often as younger babies.