Birthday Calculator
Discover your exact age, the day you were born, your next birthday countdown, and upcoming birthday milestones — all in one place.
Calculate Your Birthday
Enter your date of birth to get your personalized birthday results.
Your Birthday Results
Calendar days from your local today.
Your Upcoming Birthday Milestones
Explore selected milestone birthdays that are still ahead, based on today's local calendar date.
What Is a Birthday Calculator?
A birthday calculator uses your date of birth to work out your calendar-based age and other useful birthday details. Depending on your selected reference date, it can show your completed years, months and days, your birth weekday, and how long it is until your next birthday.
How to Use This Birthday Calculator
- Enter your date of birth.
- Keep the reference date set to today or select another date to calculate your age on that day.
- Choose your preferred date format and, if relevant, your 29 February birthday convention.
- Select Calculate Birthday to view your results and upcoming milestones.
How Is Exact Age Calculated?
Age is calculated using calendar years, months and days, rather than estimating every year as 365 days or every month as 30 days. The calculator counts completed years first, then completed calendar months, and finally the remaining days. Total days are calculated separately from the difference between calendar dates.
How Is the Next Birthday Calculated?
The calculator compares today's local calendar date with your birthday in the current year. If that date has already arrived, it uses the next year's birthday. For a 29 February birth date in a non-leap year, you can choose 28 February or 1 March as the anniversary convention.
Frequently Asked Questions
How do I calculate my exact age?
Enter your birth date and the date on which you want to calculate your age. The calculator reports completed years, remaining months and remaining days using calendar arithmetic.
How many days are left until my next birthday?
Enter your birth date and calculate. The countdown compares your next birthday with today's local calendar date. It is independent of the optional age reference date.
What day of the week was I born?
The calculator determines the weekday from the Gregorian birth date you enter.
How does the calculator handle leap-year birthdays?
For a 29 February birthday in a non-leap year, select whether to use 28 February or 1 March as the anniversary date. Different legal or cultural contexts may use different rules.
Can I calculate my age on a past or future date?
Yes. Choose a reference date on or after your birth date. The age calculation uses that date, while the next-birthday countdown remains based on today.
Does the birthday calculator work worldwide?
It works in modern browsers worldwide and formats dates according to your selected preference. Its core calculations use Gregorian calendar dates, not every regional calendar system.
Is my birth date stored or shared?
This widget performs calculations in your browser and does not send your birth date to an external calculator service. Your website's hosting, security, analytics or other installed services may operate independently.
Does the calculator require a birth time?
No. A date of birth is sufficient for calendar-based age and birthday calculations. Exact hours lived cannot be determined from a birth date alone.