Find your exact age in years, months and days, how many days you have lived, the weekday you were born, and the countdown to your next birthday. Free, instant and private — nothing leaves your browser.
About this age calculator
This free age calculator works out the exact difference between your date of birth and any date you choose. It is handy for filling in forms that ask for age in years and months, for working out how many days old you are, for milestone birthdays, and for planning a countdown to a special date. All calculations happen locally in your browser, so your birthday is never uploaded anywhere.
Frequently asked questions
- How do I calculate my exact age?
- Enter your date of birth and the “age at” date (today by default). Your age in years, months and days appears instantly.
- How many days old am I?
- The tool shows total days lived along with weeks, months and hours.
- How is the next-birthday countdown worked out?
- It counts the whole days from the chosen date to your next birthday. Leap-day births roll to 1 March in non-leap years.
Why a year is not 365 days
Calculating age requires measuring the gap between two calendar points by subtracting the birth year, month, and day from the target date. Because months contain varying lengths of 28, 30, or 31 days, the math cannot rely on a simple division by 365. Instead, standard chronological subtraction handles the years first, then borrows days from the preceding month if the birth day exceeds the current day. This step-by-step subtraction mirrors how humans naturally count age rather than treating time as a single continuous stream of seconds.
The Gregorian calendar convention introduces complexity through leap years, which insert an extra day into February every four years to keep seasons aligned with the solar orbit. Years divisible by 100 are skipped unless they are also divisible by 400, meaning century markers like 1900 are not leap years while 2000 is. For individuals born on February 29, legal and practical traditions dictate whether their birthday falls on February 28 or March 1 during non-leap years. This adjustment ensures that everyone ages at a legally and mathematically consistent rate regardless of calendar irregularities.
The most common mistake people make when figuring age manually is assuming that all months possess an equal number of days or that dividing total days by 365 yields an accurate breakdown of years and months. Ignoring the varying lengths of individual months leads to errors of several days when bridging across months like July and August. Another frequent oversight occurs when the target date precedes the birth month within the current year, requiring a borrow from the year column that trips up manual subtraction. Using a dedicated date-arithmetic engine prevents these human calculation slips.