Age Calculator
Exact age in years, months, days
About This Calculator
An age calculator computes your exact age in years, months, and days from your date of birth to today (or any target date). It handles the complexities of varying month lengths and leap years. Exact age is used for medical screening (different guidelines apply at 40, 50, 65), insurance, eligibility requirements, and legal purposes.
Formula
Age in years = floor((Today − DoB) / 365.25)
For exact years/months/days: count full years, then full months, then remaining days
Leap year adjustment: Feb 29 birthdays are celebrated on Feb 28 or Mar 1 in non-leap years
Example Calculation
Born September 3, 1990 — age on March 16, 2026
- Full years: 1990→2026 = 35 years (Sept 3 birthday not yet reached in 2026)
- Wait — March 16 is before September 3, so age is still 35
- Months since last birthday (Sept 3, 2025): Sept→March = 6 months 13 days
Age: 35 years, 6 months, 13 days
Age Milestones and Common Significance
| Age | Milestone |
|---|---|
| 18 | Legal adulthood (US/UK), voting age |
| 21 | Legal drinking age (US) |
| 25 | Car rental discounts end; brain fully developed |
| 35 | US Presidential eligibility; increased health screenings |
| 50 | AARP eligibility; colonoscopy recommended |
| 65 | Standard Medicare eligibility (US); Social Security full benefits (born 1960+) |
Frequently Asked Questions
How is age calculated in different cultures?
In Western cultures, age is counted from birth. In traditional Korean (and some East Asian) age systems, you are born at age 1 (or 2 if born near year-end) and gain a year on New Year's Day rather than your birthday. South Korea officially adopted international age counting in 2023.
How do you handle February 29 birthdays?
People born on Feb 29 (leap day) officially age one year on that date, but celebrate on Feb 28 or Mar 1 in non-leap years. For legal purposes, Feb 28 is commonly used as the birthday in non-leap years in most jurisdictions.
What is chronological vs biological age?
Chronological age is simply calendar time since birth. Biological age reflects actual cellular and physiological aging, which varies due to lifestyle, genetics, and environment. Tests measuring telomere length, blood biomarkers, or methylation patterns estimate biological age.
How precise do I need to be for age calculations?
For casual purposes (how old am I?), year precision is fine. For medical eligibility (screening guidelines), year and month matter. For legal purposes (contracts, benefits), exact days can matter. This calculator gives all three.