Age Calculator
Pick your birth date.
If empty, 12:00 AM is assumed.
Default is today’s date.
Default is current time.
Choose how to display your age.
Updates instantly when any input changes.
Quick summary
Total days
โ
Total weeks
โ
Total hours
โ
Show step-by-step calculation
- Build two date-times: birth and on date (if time is empty, assume 00:00:00).
- Compute ฮt =
onDateTime โ birthDateTimein milliseconds. -
If unit = years / months / days, compute exact by calendar:
- Years = difference in calendar years, then months = difference in months, then days = remaining days (borrowing from previous month length when needed).
- For other units: convert ฮt into chosen unit precisely (s, min, h, d, w) using 1000, 60, 60, 24, 7.
- For months use 30.4375 days on average; for years use 365.25 days.
Unit assumptions & reference table
| Unit | Definition used |
|---|---|
| millisecond | 1/1000 of a second |
| second, minute, hour, day, week | Exact time math from your two date-times (no averaging) |
| month (avg.) | 30.4375 days (average across the calendar) |
| year (avg.) | 365.25 days (accounts for leap years) |
| years / months / days | Exact calendar difference (borrows by prior month length) |