Exact Age & Lifespan Milestone Calculator
Find your exact age in years, months and days from your date of birth, on today's date or any other date. See your total days, weeks, hours and minutes lived, your next birthday, milestone days such as your 10,000th day, and your zodiac signs. Nothing is stored or sent anywhere.
Written by Suhaib Hassan. It uses the Gregorian calendar and real month lengths. Our methodology.
It subtracts the birth date from the target date, borrowing days from the previous month when needed, so leap years and month lengths are exact.
Dividing by 365.25 drifts. This counts real calendar months and days, which is what forms and legal ages need.
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Birth year reference
Age this year, approximate days lived, the year of full retirement age (67 for anyone born in 1960 or later) and the generation, for birth years every five years.
| Birth year | Age this year | Approx. days lived | Full retirement year | Generation |
|---|
How exact age is worked out
Years, months, days
subtract year, month and day; if the day is negative, borrow the days of the previous monthLeap year rule
leap if divisible by 4, except centuries not divisible by 400Total days
days = (end date − birth date) in whole daysLeap-day birthdays
People born on 29 February celebrate on 28 February or 1 March in other years, depending on local law. This tool shows 1 March for the next birthday in a non-leap year.
Milestone days count from the date of birth, so your 10,000th day is 10,000 days after you were born.
Worked examples
Illustrative dates, each checked by hand.
Born 14 May 1995, on 5 Feb 2025
Borrowing from January.
day 5 − 14 = −9 → borrow 31 (Jan)
29 years, 8 months, 22 days
Total days
The same two dates.
= 10,860 days
= 1,551 weeks and 3 days
10,000th day
For someone born 14 May 1995.
= 29 September 2022
How to calculate your age
- Subtract your birth year from the current year to get a first estimate.
- If your birthday has not happened yet this year, subtract one year.
- For months and days, count from your last birthday to today using real month lengths.
- For total days, count the days between the two dates. This tool does all of that for you.
Legal age rules differ by country, and some traditions count age differently. For official purposes, check the rules that apply.
By Suhaib Hassan · Reviewed 29 September 2026 · How CalculatePilot verifies formulas →
Sources
- ISO 8601, Date and time — Representations for information interchange, and the Gregorian calendar leap-year rule.
- CDC National Center for Health Statistics, Mortality in the United States (life expectancy at birth).
- U.S. Social Security Administration, Full Retirement Age tables.
- Pew Research Center, generation definitions (Millennial 1981–1996, Gen Z 1997–2012).
Age in months, weeks and days
Approximate totals, using an average year of 365.25 days. Your exact figures depend on your birth date and are shown by the calculator above.
| Age (years) | Months | Weeks | Days |
|---|---|---|---|
| 1 | 12 | 52 | 365 |
| 5 | 60 | 261 | 1,826 |
| 10 | 120 | 522 | 3,652 |
| 18 | 216 | 939 | 6,574 |
| 21 | 252 | 1,096 | 7,670 |
| 30 | 360 | 1,565 | 10,958 |
| 40 | 480 | 2,087 | 14,610 |
| 50 | 600 | 2,609 | 18,262 |
| 65 | 780 | 3,392 | 23,741 |
Age difference between two people
Subtract the older birth date from the younger one using the same borrowing method. Example: one person born 3 September 1992 and another born 14 May 1995 are 2 years, 8 months and 11 days apart, which is 983 days.
Western age vs traditional Korean age
The international (Western) age used here counts completed years from the birth date. Traditional Korean age gives a newborn age 1 and adds a year every 1 January, so people are one or two years older than their international age. South Korea moved to international age for most legal and administrative purposes from 28 June 2023.
Common US age milestones
| Age | What it usually marks |
|---|---|
| 18 | Voting age in US federal elections |
| 59½ | Penalty-free withdrawals from IRAs and most 401(k) plans begin |
| 65 | Usual Medicare eligibility |
| 67 | Full Social Security retirement age for anyone born in 1960 or later |
Rules have exceptions, so check the official source for your situation.
Calculate age in Excel or Google Sheets
Use =DATEDIF(A1, TODAY(), "Y") for completed years, "YM" for the leftover months and "MD" for the leftover days, where A1 holds the birth date.
Frequently asked questions
How do you calculate exact age?
Subtract the birth date from the target date year, month and day. If the day difference is negative, borrow the number of days in the previous month and reduce the month count by one. Do the same for months and years.
How does the calculator handle leap years?
It uses the real calendar, so 29 February is included in leap years and total days are exact. A year is a leap year if divisible by 4, except century years that are not divisible by 400.
What is my 10,000th day?
It is the date 10,000 days after you were born, which falls at about 27 years and 4 months old. The tool also shows when you reach 20,000 days and one billion seconds.
What does the life progress bar mean?
It shows your age as a share of an average life expectancy, which you can edit. It is a statistical average for a group, not a forecast for any one person.
Is my date of birth stored?
No. Everything is calculated in your browser and nothing is sent to a server. The share link only puts your dates in the web address you copy.
What is the difference between Western and Korean age?
Western (international) age counts completed years from the birth date. Traditional Korean age starts at 1 and adds a year every 1 January, so it is one or two years higher. South Korea adopted international age for most legal and administrative uses on 28 June 2023.
How do I find the age difference between two people?
Subtract the older birth date from the younger one, borrowing days from the previous month when needed. For example, 3 September 1992 and 14 May 1995 differ by 2 years, 8 months and 11 days (983 days).
Why do age calculators sometimes show different days?
They borrow days from different months when the day count is negative. This calculator borrows the length of the previous month and uses the real calendar, so total days are exact either way.
How old am I if I was born on 29 February?
In leap years you have a birthday on 29 February. In other years the legal date is 28 February or 1 March depending on local law, and this tool shows 1 March.
How do I calculate age in Excel or Google Sheets?
Use DATEDIF with the birth date and TODAY(): "Y" gives completed years, "YM" the remaining months and "MD" the remaining days.
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