Age Calculator & Date Difference Calculator
Calculate exact age, days until your next birthday, total days lived, and the calendar difference between two dates without a backend.
An age calculator compares a date of birth with an as-of date to show exact age in years, months, and days.
It can also answer how many days old you are, how many days until your next birthday, and how many days are between two dates.
Use calendar dates
Enter the birth date and as-of date as full calendar dates. The result uses actual month lengths and leap years.
Pick the right mode
Use Age mode for date of birth calculations and Date difference mode for elapsed days between two dates.
Exact age = completed years + remaining months + remaining days
For age, the tool compares the birth date to the selected as-of date. It first counts completed years, then adjusts for incomplete months and days. For date difference, it compares the earlier and later date and reports both calendar difference and total days.
Leap years are included because the calculation uses actual calendar dates. For February 29 birthdays, the next birthday display is clamped to the last valid day of February in non-leap years.
Example: Someone born on January 1, 2000 is 26 years, 4 months, and 18 days old on May 19, 2026, with 9,635 total days lived.
Exact age from date of birth
Calculate age in years, months, and days for a birthday, profile, or personal record.
Days old calculator
Find total days lived from a birth date to today or another selected as-of date.
Birthday countdown
Check days until the next birthday, including leap-year birthday handling.
Date difference checks
Calculate elapsed calendar days between deadlines, milestones, trips, or event dates.
Example
May 1 to May 2 is 1 elapsed calendar day. Exact age counts completed years first, then remaining months and days.
Assumption
The calculator works with dates only. It does not include time of birth, time zone, or local legal cutoffs.
Limitation
For school, visa, insurance, or legal age decisions, confirm how the relevant organization defines the effective date.
What is an exact age calculator?
It calculates age from a date of birth to an as-of date, then reports completed years, remaining months, remaining days, and total days lived.
What does exact age mean?
Exact age means the number of completed years, remaining months, and remaining days between a birth date and an as-of date.
Is the end date included in days between dates?
The total days result counts the elapsed calendar days between the two dates. For example, May 1 to May 2 is 1 day.
Can I calculate age for a past or future date?
Yes. Change the as-of date to calculate age on a historical date or a future date, as long as the birth date is not after the as-of date.
Can I calculate how many days old I am?
Yes. Enter your birth date and use today's date as the as-of date. The total days lived result shows whole calendar days elapsed.
Does this tool use an external API?
No. The calculator runs locally in the browser and does not send your dates to a server.
Suggested workflow
Date calculation path
Calculate age or elapsed days, then convert the same dates into workday or countdown planning.