Age Calculator
Work out an exact age in years, months and days, plus total days lived and time to the next birthday.
Formula
calendar-aware difference between date of birth and a reference date
Tips
- The years/months/days breakdown walks the calendar rather than assuming an average month, so it matches how people actually count.
- Someone born on 29 February has a birthday only in leap years. Most jurisdictions treat 1 March as the legal date in other years.
- Set the second date to something other than today to work out an age at a past or future point — useful for eligibility cut-offs.
Frequently asked questions
Why does the month count sometimes look off by one?
Months have different lengths. Going from 31 January to 28 February is one day short of a full month, so it counts as 0 months and 28 days rather than 1 month.