Age Calculator
Pick a date of birth and an “as of” date to get an exact age in years, months and days — plus the totals in months, weeks and days.
Example
Someone born on 1 January 1990, measured on 1 January 2025, is exactly 35 years, 0 months, 0 days old — that's 420 months or 12,784 days.
How it works
The calculator subtracts the birth date from the target date, borrowing days from the previous month and months from the year where needed, so the years/months/days are calendar-accurate (leap years included). Totals are derived from the exact number of days between the two dates.
Good to know
The Age Calculator works out how much time has passed between two calendar dates: a date of birth and an "as of" date that defaults to today. It returns your age as a precise breakdown of years, months and days, and then restates that same span as a total number of months, weeks and days. It is useful for anyone who needs an exact figure rather than a rounded estimate — parents tracking an infant's age in weeks, HR and admissions staff verifying eligibility on a specific cutoff date, or anyone filling in a form that asks for completed years.
Reach for it whenever "about 35" is not good enough. Common cases include checking the exact age someone will be on a future event date, working out a pet's or a document's age, counting how many days are left until a milestone birthday, or settling a debate about who is older down to the day. Because you can set the second date freely, it doubles as a general date-difference tool, not just a birthday counter.
Read the main result left to right — years, then months, then days — as a single combined age, not three separate quantities (someone is "35 years, 2 months and 4 days," not 35 plus 2 plus 4). The totals row is different: each value is the whole span converted into one unit, so the months, weeks and days figures are alternative ways of expressing the exact same duration. Use the years/months/days line for "how old," and the totals line for milestones like a 10,000-day anniversary.
One practical caveat: the day and week totals count actual elapsed calendar days, so they shift by one each time a 29 February falls inside the range, and "months" as a unit varies in length (28 to 31 days). If you need the count as of a particular deadline, set the "as of" date explicitly instead of relying on today, and remember the result reflects completed time, so a birthday only adds a year once the full day has passed.
Frequently asked questions
Can I calculate age on a future or past date?
Yes — change the ‘as of’ date to any date. It defaults to today, but you can set a future birthday or a historical date.
Does it handle leap years?
Yes. The day and month math uses the real length of each calendar month, so 29 February and leap years are handled correctly.
What do the totals mean?
Beyond years/months/days, it shows the same span expressed entirely in months, in weeks, and in days — handy for milestones.
Is my data uploaded anywhere?
No. Everything is calculated in your browser with JavaScript — nothing is sent to a server, so it's private and works offline once loaded.
Is this calculator free?
Yes, completely free with no sign-up and no limits.
People also ask
How do I calculate my exact age in years, months and days?
Enter your date of birth and leave the second date set to today, or pick any target date. The calculator subtracts one date from the other and shows the result as years, months and days combined, which together represent your exact age.
How many days old am I?
The tool shows your age expressed entirely in days as one of its totals. It counts every actual calendar day between your birth date and the chosen date, including the extra day added in each leap year that falls within the range.
Can I use this to find the number of days between two dates?
Yes. Although it is labelled an age calculator, you can put any earlier date in the first field and any later date in the second, and the totals will give you the difference in months, weeks and days.
Why does my age in months not equal my years multiplied by twelve?
The combined years/months/days result already separates whole years from the leftover months, while the standalone months total converts the entire span into months. They describe the same duration in two different formats, so the numbers will look different but are consistent.
Does the age calculator account for time zones or the time of day?
No. It works with whole calendar dates only and does not factor in hours, minutes or time zones, so the result reflects completed days between two dates rather than an exact moment.
How is someone born on 29 February handled?
The calculation uses the real length of each calendar month, so a 29 February birth date is handled correctly. In non-leap years the day count simply rolls over according to the actual number of days in February and the surrounding months.
Will this calculator save or share my birth date?
No. All calculations run locally in your browser using JavaScript, so your dates are never uploaded to a server and the tool continues to work offline once the page has loaded.
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