How age is calculated
Age in completed years is the number of birthdays that have passed. For the months and days, the calculator counts whole calendar months from your last birthday, then the days left over. When the day of the month hasn't come round yet, it borrows the length of the previous month, the same way you'd count on a calendar.
Worked example
Someone born on March 14, 1992 turns 34 on March 14, 2026. From then to October 14 is 7 whole months, and from October 14 to October 21 is 7 days. On October 21, 2026 they are 34 years, 7 months and 7 days old.
Leap-day birthdays
People born on February 29 have a calendar birthday only once every four years. In other years this calculator treats March 1 as the birthday. Laws differ on which date counts for legal purposes, so check local rules for things like licenses and contracts.
Ages that matter in the U.S.
- 18: legal adult in most states; eligible to vote.
- 21: legal age to buy alcohol and, under federal law, tobacco.
- 59½: withdrawals from IRAs and 401(k)s generally avoid the 10% early-withdrawal penalty.
- 62: earliest age to claim Social Security retirement benefits, at a reduced amount.
- 65: usual age of Medicare eligibility.
- 67: full Social Security retirement age for people born in 1960 or later.