Age Calculator
Calculate exact age in years, months, and days from a date of birth. Shows total days lived and days until next birthday.
Your Age
36 years 3 months 22 days
Total Days
13,263
Total Weeks
1,894
Total Months
435
Next Birthday
251d to go
How to use this calculator
- Click the date field and select your date of birth.
- Your exact age appears instantly in years, months, and days.
- Scroll down to see total days lived, total weeks, and how many days until your next birthday.
How Age Is Calculated: Beyond Just Counting Years
Legal, medical, and administrative contexts often need exact age in years and months — not just whole years. This tool decomposes the interval into years, remaining months, and remaining days.
The approach follows ISO 8601 calendar periods (the rule behind Java’s Period.between): full years, then full months, then the remaining days, with month ends clamped (Jan 31 + 1 month = Feb 28) so the result is never negative. The one deliberate difference: a Feb 29 birthday is celebrated on Mar 1 in common years.
Total days lived and countdown to the next birthday are useful for planning and milestones. This calculator handles edge cases like Jan 31 → Feb correctly.
How exact age is calculated
Age is counted the way people and official forms count it: first the number of whole years since the birth date, then whole months, then the remaining days. When a month is shorter than the birth day — someone born on 31 January has no “31st” in February — the month is counted as complete on its last day, so the result is never negative or impossible.
Everything uses the calendar date on your device, so the answer changes at your local midnight, not at midnight UTC.
Worked examples
- Born 20 May 1990, on 1 October 2026: 36 years, 4 months and 11 days.
- Born 31 January 1990, on 1 March 2026: 36 years, 1 month and 1 day — February counts as a full month on the 28th.
- Born 29 February 2000: on 28 February 2025 the age is 24 years, 11 months and 30 days; on 1 March 2025 it is exactly 25. In common years the birthday is treated as 1 March.
- Born 1 January 2000: the 10,000th day after birth falls on 19 May 2027, at an age of 27 years, 4 months and 18 days.
When the exact age matters
- Eligibility cut-offs: school entry, sports age groups, retirement and pension ages are often defined as an age reached by a specific date. Enter the date of birth and check against the cut-off date.
- Children’s growth and development: paediatric growth charts and milestones are given in months for young children, which the total-months figure provides directly.
- Legal ages differ in how a 29 February birthday is treated in common years — some jurisdictions use 28 February, others 1 March. For a legal deadline, check the local rule.
- East Asian age reckoning: the traditional Korean and Chinese systems count a newborn as one year old. South Korea standardised on international age for legal and administrative purposes in June 2023. This calculator uses international age.
Privacy
Your date of birth is processed only in your browser and is not stored or sent anywhere. Closing or reloading the page clears it.
Total days, weeks and months
Total days is the number of calendar days that have passed since the birth date, leap days included — 0 on the day of birth. Total weeks is that number divided by 7 and rounded down, and total months is years × 12 plus the extra months. Days until the next birthday is 0 on the birthday itself, so a countdown never skips the day you are celebrating.
Related tools
These free tools pair well with this page — open them in a new tab to finish your workflow.
Frequently Asked Questions
How is the exact age calculated?
The calculator subtracts your birth date from today's date using calendar arithmetic. Years are counted first, then the remaining months, then the remaining days — matching how age is officially recorded on documents.
Why does my age show in years, months and days?
Most people only know their age in whole years, but breaking it down into months and days gives you a more precise answer — useful for legal forms, medical records, or just satisfying curiosity.
How is 'total days lived' calculated?
It is the number of calendar days that have passed between your birth date and today, including every leap day — 0 on the day you were born, 365 on a first birthday in a common year.
What is the 'days until next birthday' count?
The tool finds the next occurrence of your birth month and day (in the current or next year) and counts the days from today to that date. If today is your birthday, it returns 0.
Does this work for any birth date?
Yes, any past date is supported. Dates very far in the past may differ slightly from historical calendars because the tool uses the proleptic Gregorian calendar throughout.
What is the 10,000 days milestone?
Reaching 10,000 days alive (roughly 27 years and 4–5 months) is a popular personal milestone. Compare it with the total days lived: once that figure passes 10,000, you have reached it. Someone born on 1 January 2000 reaches it on 19 May 2027.
How does age calculation handle leap year birthdays (Feb 29)?
When your birthday falls on Feb 29 and the current year is not a leap year, the calculator treats March 1 as your birthday for the purposes of counting age and days until next birthday.