Age
calculator.
Find an exact age in completed years, months and days on any date, with totals in months, weeks and days and a countdown to the next birthday.
Exactly how old,
and why.
- Age is counted in completed units: whole years first, then whole months, then the remaining days.
- A month is completed on the same day number in the next month. If that day does not exist (for example the 31st), the last day of the month counts.
- For someone born on 29 February, you choose whether the birthday falls on 28 February or 1 March in common years. The default is 28 February.
- Only calendar dates are used, never times of day or time zones.
How is exact age calculated?
Start from the date of birth and count how many complete birthdays have passed. That is the age in years. From the most recent birthday, count complete months: a month is complete on the same day of the next month. Whatever is left over is the number of days.
For example, someone born on 15 June 1990 is 36 years, 4 months and 23 days old on 7 November 2026. Their 36th birthday was 15 June 2026, four more months take us to 15 October 2026, and 15 October to 7 November is 23 days.
What happens with month ends?
When the birth day number does not exist in a later month, the last day of that month is used. Someone born on 31 January completes their first month on 28 February (29 February in a leap year). This is the same month-end rule our date calculator uses. Other calculators sometimes borrow days from the previous month instead, so results for month-end birthdays can differ by a day or two between tools. The total days figure is unaffected because it does not use months.
When does someone born on 29 February have a birthday?
In leap years, on 29 February. In common years there is no single answer. In Scotland, the Age of Legal Capacity (Scotland) Act 1991 treats the birthday as 1 March. In Newfoundland and Labrador the law uses the last day of February. The law of England and Wales does not settle the question. Many people celebrate on 28 February.
The calculator therefore lets you choose. The choice only affects whether a 29 February birthday is reached on 28 February or on 1 March. For legal decisions such as eligibility ages, check the rule that applies where you live.
Why is age in days or weeks useful?
Totals avoid month-length ambiguity entirely. They are useful for milestones (10,000 days old), for infant ages, which are often given in weeks, and for checking other results. Total days is simply the number of days from the date of birth to the chosen date.
total days = age-on date − date of birth
total weeks = ⌊total days ÷ 7⌋, remainder = total days mod 7Worked examples.
A typical age
Born 15 June 1990. How old on 7 November 2026?
36 years, 4 months and 23 days. That is 13,294 days, and the next birthday is 15 June 2027.
Load this exampleA 29 February birthday (28 February rule)
Born 29 February 2000, measured on 28 February 2025 using the 28 February rule.
Exactly 25 years: the birthday is reached on 28 February.
Load this exampleThe same birthday under the 1 March rule
The same dates, but using the 1 March rule (as in Scotland).
24 years, 11 months and 30 days: the 25th birthday is the next day, 1 March 2025.
Load this exampleA month-end birth date
Born 31 January 1985, measured on 1 March 2026.
41 years, 1 month and 1 day. The month was completed on 28 February 2026.
Load this exampleA newborn in weeks
Born 1 October 2026, measured on 7 November 2026.
37 days, which is 5 weeks and 2 days (1 month and 6 days).
Load this exampleWhat this calculator
does not do.
- It does not use the time of birth, so on the birthday itself the age changes at midnight rather than at the hour of birth.
- It uses the Gregorian calendar for all dates. Very old historical dates recorded in the Julian calendar need converting first.
- It is not a legal determination of age. Laws for eligibility, retirement or 29 February birthdays vary by jurisdiction.
- It does not calculate age in other calendar systems, such as the East Asian age reckoning.
Common questions.
How do I calculate my age on a past or future date?
Change the “Age on this date” field. It defaults to today's date on your device.
Why do two age calculators give different months and days?
They may handle month ends differently. We count a month as complete on the same day number of the next month, or on the last day of a shorter month. The total number of days is the same in every correct calculator.
Is a person born on 29 February a year older on 28 February or 1 March?
It depends on the jurisdiction and purpose. Choose either rule in the calculator. The default is 28 February.
Does the calculator store my date of birth?
No. The calculation runs in your browser and your date of birth is never added to the page address, so it does not reach our server logs or analytics. That also means a copied link does not include it: whoever opens the link enters their own date.
- Age of Legal Capacity (Scotland) Act 1991, section 6 — 29 February birthdays treated as 1 March in common years
- Family Law Reform Act 1969, section 9 (England and Wales) — age attained at the start of the relevant anniversary
- Newfoundland and Labrador, Age of Majority Act, section 3 — uses the last day of February
- Oracle Java SE 21 — LocalDate (month-end adjustment, ISO calendar)
The calculation runs entirely in your browser using whole calendar dates. Our test suite checks it against independently computed vectors, including leap-day birthdays under both rules, month-end births, same-day results and randomized consistency checks (birth date + years + months + days always reproduces the chosen date).