Calculators
Age Calculator
Calendar-accurate age — years, months, days, the weekday you were born, and how long until the next cake.
In short
Calculate exact age in years, months and days from a date of birth — plus total weeks, total days, the weekday you were born, and a next-birthday countdown.
By NaveenKumar T · Updated
- Exact Y/M/D age (calendar-true)
- Total months, weeks & days
- Day of the week you were born
Runs entirely in your browser — nothing you paste or open here is uploaded, logged, or stored.How we handle data →
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More than a birthday trick
Exact age computations show up in serious paperwork: immigration forms wanting age at the date of application, school admissions with cutoff-day rules, pension eligibility measured to the day. The 'as of' field exists precisely for these — set it to the deadline date and read the age the authority will compute.
The fun facts have their uses too: the born-on weekday settles family debates, total days converts neatly into '10,000-day' milestones, and the next-birthday countdown is honest even across leap years. Everything derives from two dates and runs entirely in your browser.
Worked example: two ages as of 10 September 2026
Two dates of birth, both measured as of 10 September 2026. The first row's 10,340 total days breaks down as 28 complete years of 365 days (10,220 days) plus 7 leap days (2000, 2004, 2008, 2012, 2016, 2020 and 2024 fall within the span) plus 113 days into the 29th year — 10,220 + 7 + 113 = 10,340:
| Date of birth | Age | Total days | Next birthday | Born on a |
|---|---|---|---|---|
| 20 May 1998 | 28 years, 3 months, 21 days | 10,340 days | in 252 days | Wednesday |
| 23 Nov 2015 | 10 years, 9 months, 18 days | 3,944 days | in 74 days | Monday |
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Frequently asked questions
Everything you need to know about the Age Calculator.
01How does the calculator handle a 29 February birthday?
In a common (non-leap) year, the next birthday for someone born on 29 February lands on 1 March, not 28 February — the date arithmetic rolls the missing day forward rather than back, so the age and the countdown both flip over on 1 March in years without a 29th of February. Every fourth 'birthday' is the real one, on the actual 29 February.
02How is exact age calculated across different month lengths?
By calendar borrowing, the way registrars do it: subtract day, month and year columns, borrowing real month lengths when a column goes negative — someone born Jan 31 turns 'one month old' on Feb 28/29, not after a fixed 30 days. Leap years are handled exactly; totals count actual elapsed days.
03Why do different sites give me a different 'age in months'?
Some divide total days by 30.44 (an average), which drifts from the calendar answer by a day or two around month ends. This tool counts true calendar months and shows total days separately — if a form asks for one or the other, both exact numbers are here.
04Why do total weeks and total months not multiply back to the same number?
Total weeks is total days divided by 7 and rounded down, and total months is years × 12 plus the remainder months — two different, exact counts derived independently from the calendar, not from each other. Multiplying total months by roughly 4.35 weeks/month gives an approximation, not the total-weeks figure; use whichever exact total the form actually asks for.
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