How it is calculated
Your age goes up by one on each birthday. This is the only way age is counted in the US.
Age = this year − birth year (minus 1 if your birthday hasn’t come yet) Months and days = months and days since your last birthday Days lived = today − date of birth (in days) Milestone date = date of birth + milestone age (59½ = 59 years and 6 months)
- For a February 29 birthday, February 28 is used in non-leap years. Some states and agencies use March 1 instead.
- When adding months lands on a date that doesn’t exist (for example, August 31 + 6 months), the last day of that month is used.
US age milestones
| Age | What changes | Basis |
|---|---|---|
| 18 | Voting in federal, state and local elections; adulthood in most states | 26th Amendment (voting age) |
| 21 | Buying alcohol in every state | National Minimum Drinking Age Act (1984) |
| 26 | Coverage as a child on a parent’s health plan ends (you can stay on until you turn 26) | Affordable Care Act |
| 50 | 401(k) and IRA catch-up contributions from the year you turn 50 ($8,000 for a 401(k) in 2026) | IRS |
| 59½ | No 10% early-withdrawal penalty on 401(k) and IRA withdrawals | IRS |
| 62 | Earliest (reduced) Social Security retirement benefits | SSA |
| 65 | Medicare eligibility | Medicare.gov |
| 66–67 | Social Security full retirement age (by birth year) | SSA |
| 73 or 75 | Required minimum distributions begin (73 if born 1951–1959, 75 if born 1960 or later) | SECURE 2.0 Act |
Social Security full retirement age
| Year of birth | Full retirement age |
|---|---|
| 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 and later | 67 |
SSA table. If you were born on January 1, use the previous year. For people born in 1960 or later, claiming at 62 cuts benefits by up to 30%.
Example: born July 15, 1990
If today is October 21, 2026:
- Exact age: 36 years, 3 months, 6 days
- Days lived: 13,247
- Next birthday: Thursday, July 15, 2027 — 267 days away
- Age 59½: January 15, 2050
- Full retirement age 67: July 15, 2057
- RMDs begin at 75: July 15, 2065 (the first one is due by April 1 of the following year)
Things to keep in mind
- Social Security treats you as reaching an age on the day before your birthday, and people born on the 1st as born in the previous month. Check the month your benefits can start in your my Social Security account.
- Medicare eligibility starts on the 1st of the month you turn 65 (the month before if your birthday is on the 1st), and the initial enrollment period runs seven months: three before, that month and three after.
- Coverage on a parent’s plan usually ends on your 26th birthday, though some plans continue it to the end of that month or year.
- The statute is ambiguous for people born in 1959; following the IRS’s 2024 proposed regulations, their RMD age is calculated as 73.
- This table explains the rules; it is not advice on when to claim benefits or withdraw money.
FAQ
Is age in the US always counted from your birthday?
Yes. Laws, contracts, medical care and insurance all use your age as of your last birthday.
When exactly is age 59½?
Six months after your 59th birthday. Someone born on July 15, 1990, reaches it on January 15, 2050.
What happens if I claim Social Security after full retirement age?
Benefits grow for each month you wait past full retirement age, up to age 70 (8% a year for people born in 1943 or later). There’s no further increase after 70.
When is my first RMD due?
By April 1 of the year after you reach your RMD age, then by December 31 every year after that. Roth IRAs have no RMDs during the original owner’s lifetime.