How to use this age calculator
- Enter the date of birth. Use the date picker or type the date; it works for any date from 1600 onward.
- Check the “age at this date” field. It starts at today’s date on your device. Change it to find someone’s age on a past or future date, such as a school cutoff or a retirement date.
- Read the results: age in completed years, months and days, totals in other units, the day of the week of the birth and how many days remain until the next birthday.
- Share or save the result with “Copy link to results”; the link keeps both dates.
How age is calculated
In the U.S. (and most of the world) age is counted in completed years: you are a year older only once the anniversary of your birth date arrives. Months and days are counted the same way, from your most recent birthday forward.
Age = current year − birth year − b, where b = 1 if this year's birthday hasn't happened yet, otherwise 0
- Y now
- year of the date you are measuring to
- Y birth
- year of birth
- b
- 1 if the birthday has not yet occurred that year, otherwise 0
Worked example
Born Friday, June 15, 1990, measured on Tuesday, September 29, 2026: 2026 − 1990 = 36. The 2026 birthday (June 15, 2026) has already passed, so b = 0 and the age is 36 years. From the last birthday, June 15, 2026, there are 3 whole months and then 14 more days, for an exact age of 36 years, 3 months, 14 days. Counting every calendar day, including leap days, that is 13,255 days.
When a month is shorter than your birth day, the calculator counts that month as complete on its last day. Someone born January 31 is exactly one month old on February 28 (or 29), and two months old on March 31. All math runs on calendar dates only, so the answer never shifts with your time zone.
Age in months, weeks, days and hours
Totals depend on how many leap days fall between two dates, so they differ slightly from simple multiplication. These are exact figures at each birthday for someone born on June 15, 1990. Hours are days × 24 and ignore the time of birth and daylight saving time.
| Age (years) | Months | Weeks | Days | Hours |
|---|---|---|---|---|
| 1 | 12 | 52 + 1 d | 365 | 8,760 |
| 10 | 120 | 521 + 6 d | 3,653 | 87,672 |
| 18 | 216 | 939 + 2 d | 6,575 | 157,800 |
| 21 | 252 | 1,095 + 5 d | 7,670 | 184,080 |
| 30 | 360 | 1,565 + 3 d | 10,958 | 262,992 |
| 40 | 480 | 2,087 + 1 d | 14,610 | 350,640 |
| 50 | 600 | 2,609 | 18,263 | 438,312 |
| 65 | 780 | 3,391 + 4 d | 23,741 | 569,784 |
| 100 | 1,200 | 5,217 + 6 d | 36,525 | 876,600 |
Leap-year birthdays (February 29)
About one day in 1,461 is a February 29, so leap-day birthdays are rare but real. In the three common years out of every four, this calculator uses February 28 as the birthday: the last day of the birth month, the same rule it applies to every month-end birth date. So someone born on February 29, 2000 turned 25 on Friday, February 28, 2025, and on February 27, 2025 was 24 years, 11 months, 29 days old.
Not everyone uses that convention: the other common choice is March 1, the day after February 28. Either way the age is the same for the other 364 days of the year; only that one day differs. If an exact legal date is at stake, check the rule used by the agency or business involved.
Legal and retirement age milestones in the U.S.
| Age | Milestone | Rule |
|---|---|---|
| 18 | Right to vote in federal and state elections | 26th Amendment to the U.S. Constitution |
| 62 | Earliest age for reduced Social Security retirement benefits | 42 U.S.C. 416(l) (“early retirement age”) |
| 65 | Medicare eligibility for most people | Medicare.gov |
| 65–67 | Social Security full retirement age, by birth year | 42 U.S.C. 416(l) |
| 73 or 75 | Required minimum distributions from IRAs and 401(k)s begin (75 if born in 1960 or later) | IRS final RMD regulations (2024) |
The 26th Amendment says the right to vote of citizens “eighteen years of age or older” shall not be denied on account of age. For Social Security, federal regulations say you reach an age on the day before your birthday, which is why people born on January 1 are grouped with the previous birth year. Full retirement age by year of birth:
| Year of birth | Full retirement age |
|---|---|
| 1937 or earlier | 65 |
| 1938 | 65 and 2 months |
| 1939 | 65 and 4 months |
| 1940 | 65 and 6 months |
| 1941 | 65 and 8 months |
| 1942 | 65 and 10 months |
| 1943–1954 | 66 |
| 1955 | 66 and 2 months |
| 1956 | 66 and 4 months |
| 1957 | 66 and 6 months |
| 1958 | 66 and 8 months |
| 1959 | 66 and 10 months |
| 1960 or later | 67 |
For RMDs, IRS regulations set the starting age at 72 for people born July 1, 1949 through 1950, 73 for 1951 through 1959, and 75 for 1960 or later. See how these ages fit your plans with the retirement calculator.
How old are you if you were born in…
The age you turn in 2026 is simply 2026 minus your birth year. Before your birthday you are one year younger. Each year below links to a page with that birth year’s generation, Social Security full retirement age, Medicare and RMD years and zodiac animal; the full list is on the age by birth year page.
| Born in | Before birthday | After birthday |
|---|---|---|
| 1950 | 75 | 76 |
| 1955 | 70 | 71 |
| 1960 | 65 | 66 |
| 1965 | 60 | 61 |
| 1970 | 55 | 56 |
| 1975 | 50 | 51 |
| 1980 | 45 | 46 |
| 1985 | 40 | 41 |
| 1990 | 35 | 36 |
| 1995 | 30 | 31 |
| 2000 | 25 | 26 |
| 2005 | 20 | 21 |
| 2010 | 15 | 16 |
| 2015 | 10 | 11 |
| 2020 | 5 | 6 |
Counting days between other dates
Need the number of days between two dates that aren't a birthday, or a date a certain number of days from now? Use the date calculator. For retirement timing, the retirement calculator turns your current age and savings into a projection.
Frequently asked questions
How do I calculate my exact age?
Subtract your birth year from the current year, then subtract one more if you haven't had your birthday yet this year. That gives completed years. For months and days, count whole months from your last birthday and then the remaining days. Born June 15, 1990, you are 36 years, 3 months, 14 days old on September 29, 2026.
How old am I if I was born in 1990?
If you were born in 1990, you turn 36 in 2026: you are 36 once your birthday this year has passed and 35 before it. The same rule works for any year: 2026 minus your birth year is the age you turn this year. See the age by birth year table for every year from 1940 to 2010.
How is age counted for a February 29 birthday?
This calculator treats February 28 as the birthday in common years, so someone born February 29, 2000 turned 25 on February 28, 2025 and was 24 years, 11 months, 29 days old the day before. There is no single U.S. rule for leap-day birthdays: some organizations use March 1 instead, so check with the agency or business involved when a date matters legally.
How many days old am I?
Count the days between your birth date and today, including the extra day in every leap year you've lived through. Someone born June 15, 1990 is 13,255 days old on September 29, 2026, which is 1,893 full weeks. Enter your own birth date above to see your total in days, weeks, months and hours.
What day of the week was I born?
Enter your date of birth and the calculator shows the weekday it fell on, using the Gregorian calendar for every date from 1600 onward. For example, June 15, 1990 was a Friday, and that person's next birthday, June 15, 2027, falls on a Tuesday.
At what age can I get full Social Security retirement benefits?
Full retirement age is 67 for anyone born in 1960 or later, and between 65 and 66 and 10 months for earlier birth years (see the table above). You can start reduced benefits as early as 62. Social Security treats you as reaching an age the day before your birthday, so a January 1 birthday uses the previous year's full retirement age.
At what age do you qualify for Medicare?
Most people become eligible for Medicare at 65. According to Medicare.gov, you can generally first sign up for Part A and Part B during a 7-month window that starts 3 months before the month you turn 65 and ends 3 months after it. People under 65 can qualify earlier if they have a disability, End-Stage Renal Disease or ALS.