How to use the age calculator
Enter your birth date — day, month, year — and the tool works out your exact age. Everything updates as you type, so there's no Calculate button. If you want to see how old you were on a specific date, switch to the Custom date tab and pick that date instead.
Year range
The calculator accepts any year from 1 AD to 9999 AD. This covers historical figures, genealogy work and any ancestor dating you might be doing. Dates far in the past use the proleptic Gregorian calendar — the same calendar extended backward before its official adoption in 1582.
What you get
- Years, months, days — the exact age, not just a whole number of years.
- Next birthday countdown — how many days until your next birthday, and which day of the week it falls on.
- Total units — your age in months, weeks, days, hours, minutes and seconds.
- Day of week born — the weekday of your birth.
- Western zodiac — Aries through Pisces.
- Chinese zodiac — the animal sign for your birth year.
- Life stage — infant, child, teenager, young adult, adult, middle-aged, or senior.
How age is calculated
Age isn't just the difference between two dates in days. It's counted in the calendar: first the number of full years, then the remaining full months, then the leftover days. This is why two people born 365 days apart don't necessarily have the same age — leap years and months of different lengths come into play.
Leap years
If you were born on February 29, this tool treats your birthday in non-leap years as March 1. The countdown to your next birthday works every year, including the three years out of four when there's no February 29.
Common uses
- Filling out forms — get your exact age in years, months and days.
- Milestone tracking — how many days until your 18th, 21st, 30th, or 50th birthday.
- Medical forms — exact age in months for young children matters in pediatric contexts.
- Pension and retirement planning — how long until you reach a specific age.
- Historical and genealogy work — how long ago was a specific event, or how old was a historical figure at a specific moment.
Why use this tool?
Unlike online age calculators that submit your birth date to a server, this one runs entirely in your browser. Nothing is uploaded, no account is needed, and it works offline after the first visit.
Common questions
How is age calculated?
Age is calculated by counting full years, then full months, then remaining days between your birth date and today. Leap years and months of different lengths are handled automatically.
What range of years is supported?
Any year from 1 to 9999. Historical dates work with the proleptic Gregorian calendar — the same calendar extended backward before 1582.
Why does my age in months differ from one calculator to another?
Because months have different lengths. Some calculators divide total days by 30.44 (the average month length), which gives an approximation. This tool uses real calendar months — the same way age is counted on official documents.
Does it handle leap years?
Yes. February 29 birthdays are handled with a March 1 fallback in non-leap years, and every calculation respects the real calendar.
What is my Chinese zodiac sign?
Your Chinese zodiac animal is determined by your birth year. The cycle repeats every 12 years in the order: Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, Pig. Note that the Chinese New Year falls in late January or early February, so people born in January or early February belong to the previous year's animal.
How is zodiac sign determined?
The Western zodiac sign is based on your birth month and day, following the standard date ranges used in Western astrology.
Can I calculate age on a future date?
Yes. Switch to the Custom date tab and pick a future date. The tool will show how old you will be on that day.
Is my birth date saved?
Your inputs are stored in your browser's local storage so they come back when you refresh. Nothing is sent to any server.