Age calculator: exact age in years, months and days
Enter a date of birth; the second date starts as today. The result is age in completed years, the exact age in years, months and days, the totals in months, weeks and days, the weekday of birth and how long until the next birthday.
Inputs used by this calculator
Age Calculator uses the fields below. The starting values reproduce the page example; replace them with values from the same units and time period before using the result.
| Input | Starting example | Accepted value | How it is used |
|---|---|---|---|
| Date of birth | 1990-06-15 | Text in the format shown | Supplies the date of birth quantity used by the published equation or result breakdown. |
| Age on date | 2026-09-29 | Text in the format shown | Supplies the age on date quantity used by the published equation or result breakdown. |
How age is counted
Age in the United States is counted in completed years: the number goes up on each birthday, not on January 1. Someone born on June 15, 1990 is 35 until June 14, 2026 and turns 36 on June 15, 2026. The calculator applies the same rule for any pair of dates.
Exact age in years, months and days
After the completed years, the calculator counts whole months since the last birthday and then the days left over. From June 15, 1990 to September 29, 2026 that is 36 years, 3 months and 14 days. Because months have different lengths, this breakdown is the most natural way to read an age, while the total days give an exact count.
Leap-day birthdays
People born on February 29 have a calendar birthday only in leap years. This calculator treats February 28 as the birthday in other years. Some laws and organizations use March 1 instead, so check the rule that applies if an exact legal date matters. The U.S. Naval Observatory explains the leap-year rule that decides which years include February 29.
Age on a past or future date
Change the second date to find how old someone was on a past event or will be on a future one, such as a graduation, a wedding or the first day of retirement. The answer uses the same completed-year rule, so it matches the age written on most forms.
Milestone ages in the United States
Several federal rules are tied to age. Citizens can vote in federal elections at 18. Social Security retirement benefits can start at 62 with a permanent reduction, and full retirement age is 67 for people born in 1960 or later. Most people become eligible for Medicare at 65. The table below shows those ages; confirm program details with the agency before making a decision.
Why another tool may differ by a day
Differences usually come from time zones, from counting the birth date itself, or from how February 29 is handled. This calculator works in whole calendar days, does not count the birth date as a day lived and uses February 28 for leap-day birthdays in common years.
Ages tied to U.S. federal rules
| Age | What changes | Source |
|---|---|---|
| 18 | Citizens can vote in federal elections (26th Amendment) | National Archives |
| 62 | Earliest age for reduced Social Security retirement benefits | Social Security Administration |
| 65 | Most people become eligible for Medicare | Medicare.gov |
| 67 | Full Social Security retirement age for people born in 1960 or later | Social Security Administration |
Frequently asked questions
How old am I in years, months and days?
Enter your date of birth and keep today's date; the Exact age row shows years, months and days.
How many days old am I?
The Total days row counts every day from your birth date to the second date.
What day of the week was I born?
The Born on a row shows the weekday of your birth date.
How many days until my next birthday?
The countdown row shows the days left and the date of the next birthday with its weekday.
How is a February 29 birthday handled?
In years without February 29, the calculator uses February 28 as the birthday.
Can I find someone's age on a specific date?
Yes. Change the second date to any past or future day.
Does the calculator store my birth date?
No. The calculation runs in your browser and the date is not sent anywhere.
What to keep in mind
A February 29 birthday is treated as February 28 in non-leap years.
Results are rounded for display in US format, with money in dollars and cents; CSV exports keep full calculation precision. This is a calculation summary, not an official certificate.