How to use the age calculator
- Enter the date of birth.
- Leave Age on this date as today, or change it to find an age on any other date.
- Read the exact age in years, months and days, plus the totals and the countdown to the next birthday.
How exact age is worked out
1. Count whole months from the birth date to the target date (a month is complete when the same day-of-month is reached; if that day doesn’t exist, the month’s last day is used) 2. Years = Whole months ÷ 12 (whole part) Months = Whole months − Years × 12 3. Days = Days from the last “month-versary” to the target date Total days = Target date − Birth date (including leap days)
Worked example
Born on May 15, 1990, age on October 24, 2026:
- From May 15, 1990 to May 15, 2026 = 36 years
- From May 15 to October 15, 2026 = 5 months
- From October 15 to October 24 = 9 days → 36 years, 5 months, 9 days
- That is 437 months, 1,901 weeks and 13,311 days, and the next birthday is in 203 days
Age milestones
| Milestone | Age |
|---|---|
| 10,000 days old | 27 years, 4 months (about) |
| 1 billion seconds old | 31 years, 8 months (about) |
| 20,000 days old | 54 years, 9 months (about) |
| US driving permit (most states) | 15–16 years |
| US voting age | 18 years |
| US legal drinking age | 21 years |
| Medicare eligibility | 65 years |
| US full retirement age (born 1960 or later) | 67 years |
Why months make age tricky
Months have 28, 29, 30 or 31 days, so “one month” isn’t a fixed number of days. This calculator follows the common convention used by most date libraries: a month is complete when the same date comes around again, and when a month is too short (for example, one month after January 31) the last day of that month is used. Because of this, different calculators can disagree by a day or two in the “days” part around month ends — the total number of days is always exact.
Common uses
- Forms and applications that ask for your age on a specific date.
- School entry: many US states require a child to be 5 by a cut-off date (often September 1) to start kindergarten.
- Sports age groups, which are often based on age on a set date or birth year.
- Retirement and benefits: Social Security, pensions and retirement accounts have age-based rules.
- Fun facts: find your 10,000th day or the weekday you were born.
Leap years
A leap year has 366 days. Years divisible by 4 are leap years, except century years, which are only leap years when divisible by 400 — so 2000 was a leap year but 1900 was not. The total-days figure counts every leap day between the two dates automatically.