Age calculator by date of birth
Enter a date of birth and this age calculator works out the exact age in years, months and days, plus how many days remain until the next birthday.
Last updated
How to use the age calculator
- Enter the date of birth with the date picker or by typing it.
- Leave the second date as today, or change it to find an age on another day, such as a deadline or an exam date.
- Press Calculate age.
- Read the exact age, the total number of days lived and the countdown to the next birthday.
How the age calculator works
The calculator counts whole calendar years first, then whole months, then the remaining days, the same way people say "34 years, 5 months and 12 days". Months have different lengths, so the remaining days are counted from the most recent monthly anniversary of the birth date.
Dates are handled as plain calendar days on your device, so time zones and daylight saving changes can't shift the answer by a day.
Formula
Years = the difference in years, minus 1 if this year's birthday hasn't happened yet. Months = whole months since the last birthday. Days = days since the last monthly anniversary. If that anniversary doesn't exist, such as the 31st in a 30-day month, the last day of the month is used.
Days to the next birthday = the next birthday's date − today's date. People born on 29 February have their birthday counted on 28 February in years that aren't leap years.
Example
Someone born on 15 March 1990 is 36 years, 7 months and 29 days old on 13 November 2026. Their next birthday, on 15 March 2027, is 122 days away.
By then they have lived 13,392 days, a number that includes the nine leap days since 1990.
Tips and common mistakes
Check eligibility on the cut-off date
For school entry, retirement or visa rules, set the second date to the official cut-off date rather than today.
Watch the 29 February rule
Some organisations treat 1 March as the birthday in non-leap years. Check their rules if the exact day matters.
Plan loans around milestones
Want a loan paid off before you retire? Work out the years you have left here, then try that tenure in the EMI calculator.
Adult health measures start at 18
Adult BMI categories apply from age 18. Once you know someone is an adult, use the BMI calculator.
Frequently asked questions
How is my age worked out?
Whole years are counted first, then whole months since your last birthday, then the days since the most recent monthly anniversary.
Can I find my age on a future date?
Yes. Set the second date in the future to see how old someone will be on that day.
How are leap years handled?
Leap days are included in the total days lived, and 29 February birthdays fall on 28 February in other years.
Why does the countdown say today?
If the second date is the birthday itself, the next birthday is today, and the age shown is the new age.
Is my date of birth stored?
No. Everything is calculated in your browser and nothing is saved or sent anywhere.