Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Explicit convention: February 29 clamps to February 28 in a nonleap year. Legal age rules can differ. Dates only; no birth times.
Example Calculation
- Birth date: 2000-02-29
- Reference date: 2025-03-01
A 29 February 2000 birth is 25 years and one day old on 1 March 2025 under the February-28 anniversary convention.
Frequently asked questions
How do I use this calculator?
Enter birth date, reference date. The result updates automatically. Use Reset to restore the example values.
What method does it use?
Count complete years with end-of-month clamping, then complete months, then remaining days.. Explicit convention: February 29 clamps to February 28 in a nonleap year. Legal age rules can differ. Dates only; no birth times.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.