Age calculator
Find an exact age in completed years, months and days from a birth date to any reference date, plus total days lived.
- Runs in your browser
- No upload
- Instant result
Assumptions & formula
Formula and assumptions
Y + M + D; 29/02 → 01/03
Start is the birth date; end is the reference date. A Feb 29 birthday advances on Mar 1 in non-leap years. Month anniversaries clamp to the last day of shorter months. No hours or timezone inferred.
Results
Enter values and press Calculate to see the result here.
How to use this calculator
- Set inputs and units
Enter a birth or start date and an explicit reference date. The reference date can't be earlier than the birth date.
- Calculate
Check this worked example: 2000-06-15 → 2026-07-20: 26 years +1 month +5 days; totalDays=9531
- Results
Completed years and months are calendar components. The total number of days is a separate count of elapsed days.
Questions and limits
How is a February 29 anniversary handled?
In a non-leap year the model uses March 1. Later month anchors are clamped to the last valid day of the month.
Which input errors should I correct?
Check the date order and whether leap days are valid. Don't approximate a calendar year as 365 days.
What does this calculation leave out?
A calendar age model. It is not legal age eligibility, a medical assessment or a jurisdiction-specific anniversary policy.