How it works
The calculator counts full years first, then the full months left over, then the remaining days. This is the same way people count birthdays, so the result matches what you would say out loud.
To get the months and days, the calculator steps forward one whole month at a time from the birth date and stops before it would pass the target date. The days left over are counted exactly. For example, from 20 March to 5 May is 1 month and 15 days, because 20 April has passed but 20 May has not.
When the start date is the 29th, 30th or 31st, shorter months count their last day instead. So 31 January plus one month is the last day of February.
Totals in days and weeks are an exact count of calendar days between the two dates, including leap days.
Worked example
Someone born on 15 June 1995 who checks their age on 28 September 2026 has had 31 birthdays, the last one on 15 June 2026.
From 15 June to 15 September is 3 full months, and from 15 September to 28 September is 13 days. So their age is 31 years, 3 months and 13 days.
Good to know
- People born on 29 February celebrate on different days in different countries during non-leap years. This calculator counts their birthday as 28 February in those years.
- Some cultures count age differently, for example starting at one at birth. This tool uses the international standard that starts at zero.
- Legal age for documents, school entry or retirement can follow special rules in your country. Check the official rule when it matters.
Questions people ask
How do I calculate my age in days?
Enter your date of birth and leave the second date as today. The total days row shows the exact number of days you have been alive, counting leap days.
Can I find someone’s age on a past or future date?
Yes. Change the second date to any day, for example an exam date or a visa appointment, and the age updates instantly.
Why does my age in months look different on other sites?
Some sites divide total days by an average month length of about 30.44 days. This calculator counts whole calendar months, which matches how months are counted on calendars and documents.
Is my date of birth stored?
No. The calculation happens in your browser and your date of birth is never sent or saved.