Age Calculator
Your exact age in years, months and days — plus total days, weeks and hours lived, the day you were born on, and the countdown to your next birthday.
Age counts completed calendar years, then completed months, then days — the way official documents do.
How the age calculator works
Age counts completed calendar years, then completed months, then days — the way official documents do. Someone born on 29 February has a birthday on 28 February (or 1 March in some jurisdictions) in non-leap years; this calculator uses 28 February.
Formula: age = completed years, months, days from birth date to the date chosen
Worked examples
| Inputs | Age | Note |
|---|---|---|
| born 15 June 1990, on 1 Sep 2026 | 36 years, 2 months, 17 days | 36 years, 2 months, 17 days |
| born 29 Feb 2000, on 28 Feb 2026 | 25 years, 11 months, 30 days | 25 years, 11 months, 30 days — the birthday falls on 28 Feb |
FAQFrequently asked questions
How is age calculated exactly?
Completed years first, then completed months, then the remaining days — so it can be 36 years 2 months 17 days.
When does a leap-day baby have a birthday?
In non-leap years most countries treat 28 February (some 1 March) as the birthday; this calculator uses 28 February.
What is "age in decimal years"?
Days lived divided by the average Gregorian year of 365.2425 days — used in some medical and actuarial tables.
Why do the hours look so large?
A 36-year-old has lived about 13,000 days, which is over 300,000 hours.
Does it work for future dates?
Yes — pick any second date to see how old someone will be then.
Where these figures come from
- ISO 8601 — Date and time — Representations for information interchange — the yyyy-mm-dd format and the week-numbering rules used here
- US Naval Observatory — Calendars — the Gregorian leap-year rule
- US Office of Personnel Management — federal holidays — federal holidays (not applied here)
Last checked: September 2026. The Gregorian calendar rules do not change; working-day counts exclude Saturdays and Sundays only.