Newborn babies will use between 10 to 12 diapers per day so in that first month they may use around 300 to 360 diapers in one month.
As the baby gets older as in 1 year old then they may only use 5 or 7 diapers per day which would equate to 150 to 210 diapers per month.
So if you take 150 and multiply that by 12 months you would get 1,800 diapers per year or if the baby uses 7 diapers per day that would mean that the baby would use 2,520 diapers per year.
So you can expect a baby to use between 1,800 to 2,500 and maybe even 3,000 diapers per year depending on how many diapers the baby or toddler goes through and how often the baby or toddler needs changed or gets changed.
Some parents change their babies and toddlers more often than others so one baby or toddler might go through more diapers per year than another one.