Free online calculator
Age calculator
Find exact age between dates.
Calculate exact age
Enter a date of birth and a base date to get years, months, days, weeks, and total days.
How to use this calculator
- 1
Enter date of birth
Type or pick the birth date using the date input.
- 2
Set the base date
Leave it as today or choose a past or future date to calculate age on that day.
- 3
Read the result
The calculator shows years, months, and days along with total weeks and total days.
- 4
Check edge cases
If the date of birth is later than the base date an error message appears — swap the dates to fix it.
Formula
Years: count full calendar years between the two dates.
Remaining months: count full months after subtracting the years.
Remaining days: leftover days after subtracting years and months, adjusted for the actual days in the relevant month.
Total days: (base date − date of birth) in milliseconds ÷ 86 400 000
Total weeks: ⌊total days ÷ 7⌋
Worked example
Someone born on 1990-06-15, age on 2026-04-24:
Full years: 2026 − 1990 = 36, minus 1 because June 15 has not arrived in 2026 yet → 35 years. Remaining months: April back to June = 10 months. Remaining days: 24 − 15 = 9 days. Total days: 13 097. Total weeks: 1 871.
FAQ
How is age calculated in years, months, and days? +
The calculator counts full years first, then full months in the remaining period, then the leftover days. It adjusts for the varying number of days in each month so the result matches what a calendar shows.
Does it handle leap years? +
Yes. When counting the leftover days it looks up the actual number of days in the relevant month, including February in leap years, so the result is always calendar-accurate.
Can I calculate age on a past or future date? +
Yes. Change the base date to any date after the date of birth and the calculator will show the age on that specific day. This is useful for legal or milestone calculations.
What happens if I enter a future date of birth? +
If the date of birth is after the base date the calculator shows an error. Make sure the birth date comes before the base date.
Why use total days and total weeks? +
Some milestones — like a 1000-day birthday or a pregnancy due date — are easier to think about in total days or weeks rather than years and months.
About this calculator
This age calculator finds the exact difference between two dates as years, months, and days, plus total weeks and total days. Use it to check someone's current age, calculate age on a specific date, or measure the exact time between any two milestones.
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