UtilibyWritten by the Utiliby editorial team · Last updated October 17, 2026 · Rules and formulas reviewed October 2026
What this free age calculator does
How old are you, exactly? Most people know their age in years, but forms, fun facts and milestones often need more. How many months and days have passed since your last birthday? How many days until the next one? On what day of the week were you born? An age calculator answers all of these from a single date of birth.
This free online tool goes beyond a basic year count. It gives your exact age in years, months and days, then the total months, weeks, days, hours, minutes and seconds lived. A ring shows your progress to the next birthday. You can change the Age at date to calculate age on any past or future day, which is useful for school entry, retirement planning, sports categories and history questions. The second tab shows your age on the other planets and the dates of milestones such as 10,000 days and one billion seconds. The third tab compares two people. Nothing is sent to a server.
How to use the age calculator
- Enter your date of birth. Use the date picker or type it.
- Choose the Age at date. It starts as today. Change it to see your age on another day.
- Read the result. You get years, months and days, the totals, your birth weekday and the countdown to your next birthday.
- Explore. Open the second tab for planets and milestone dates, and the third to compare two people.
- Save. Copy the result, download a CSV or print a one-page summary.
How exact age is calculated
Age is counted in whole calendar units. First count the complete years between the birth date and the chosen date, which is the number of birthdays passed. Then count the complete months since the last birthday, and finally the days left over. The months are found by moving the birth date forward one month at a time, and if a month is shorter than the birth day, the date is clamped to that month's last day, so 31 January plus one month is the end of February.
| Birth date | Age at date | Result |
|---|---|---|
| 15 Jun 1990 | 17 Oct 2026 | 36 years, 4 months, 2 days |
| 31 Jan 2020 | 1 Mar 2021 | 1 year, 1 month, 1 day |
| 29 Feb 2000 | 28 Feb 2025 | 25 years, 0 months, 0 days |
| 1 Jan 2000 | 1 Jan 2026 | 26 years, 0 months, 0 days |
Total days are found by counting calendar days directly. Weeks are days divided by seven, and hours, minutes and seconds multiply the days by 24, 1,440 and 86,400. Because the tool does not know the hour you were born, those three are approximate.
Leap years and 29 February birthdays
A leap year has 366 days. Years divisible by four are leap years, except century years that are not divisible by 400, so 2000 was a leap year and 1900 was not. A person born on 29 February has a real birthday only every four years. In other years, countries and organisations use different conventions. Some treat 28 February as the birthday and others use 1 March. This calculator counts 28 February and the countdown follows that rule. If the date matters for a legal purpose, such as the age to drive or vote, check the rule in your country.
Your age on other planets
A year is the time a planet takes to orbit the Sun. Mercury completes an orbit in about 88 Earth days and Neptune in about 165 Earth years, so the same person has very different ages on each. To find your planetary age, divide the days you have lived by 365.2425 to get Earth years, then divide by the planet's orbital period in Earth years. A 36-year-old Earth resident would be about 19 on Mars, 3 on Jupiter and about 150 on Mercury. The values come from the NASA planetary fact sheet and are a fun way to introduce children to astronomy.
| Planet | Orbital period (Earth years) |
|---|---|
| Mercury | 0.241 |
| Venus | 0.615 |
| Mars | 1.881 |
| Jupiter | 11.86 |
| Saturn | 29.45 |
| Uranus | 84.02 |
| Neptune | 164.79 |
Milestone birthdays and days-old dates
Birthdays are not the only milestones. Many people enjoy marking the day they turn 10,000 days old, which falls at 27 years and about four months. At 365.25 days a year, 10,000 days is 27.4 years, 20,000 days is 54.8 years and 30,000 days is 82.1 years. One billion seconds is 11,574 days, or about 31 years and eight months. The milestone table gives the exact dates and marks those already passed. Enter your own number to find any other date, for example 5,000 days for a child.
When you need an exact age
- School and childcare. Cut-off dates for starting school are based on age on a set day.
- Sports and competitions. Age groups often use age on 1 January or on the event date.
- Retirement and benefits. Eligibility ages are counted in years and months.
- Insurance and finance. Premiums and products depend on age at a given date.
- Travel and legal. Age limits for tickets, driving, drinking and voting.
- Family history. Work out how old a relative was at a historical event.
- Pets and anniversaries. Count time since adoption, a wedding or a start date.
Generations and traditional Korean age
The generation label uses the Pew Research Center ranges, which are widely cited in news and research: Baby Boomers (1946 to 1964), Generation X (1965 to 1980), Millennials (1981 to 1996), Generation Z (1997 to 2012) and Generation Alpha (2013 onwards). They are conventions rather than strict rules, and other organisations draw slightly different lines.
The traditional Korean age counts a baby as one year old at birth and adds a year every 1 January, so a person's age is the current year minus the birth year plus one. South Korea adopted the international age system for most official uses in June 2023, but the older count is still part of culture, which is why many people search for it.
Tips for accurate results
- Check the date format. Use the picker to avoid day and month mix-ups.
- Use the right Age at date. For a form that asks for age on a given day, change the date and do not use today.
- Remember time zones. The calculator uses calendar dates, so a birth late at night in another time zone may count as the next day on local records.
- Keep proof. For official forms use the age stated on your documents.
Privacy, accuracy and responsible use
Your date of birth is personal information. This tool processes it in your browser and does not store or send it. The results use the Gregorian calendar and the standard method of counting complete years, months and days. The planetary ages and generation labels are for interest only. For legal, medical or official purposes, rely on certified documents and the rules of the authority concerned.
Related free tools
Use these free online tools together with this one:
- Count the days, weeks and months between any two dates with the days between dates calculator.
- Work out how far through a year or a goal you are with the percentage calculator.
- Find your sun sign from your birth date with the zodiac sign calculator.
- See the moon phase on the day you were born with the moon phase calculator.
Frequently asked questions
What is an age calculator?
A tool that works out how old someone is from their date of birth, in years, months and days, and often the total days lived and the date of the next birthday. This one also shows your age on other planets and compares two people.
How do I calculate my exact age?
Enter your date of birth. The calculator counts the full years, then the full months since your last birthday, then the leftover days. You can also change the Age at date to see how old you were or will be on any day.
How does the calculator handle months of different lengths?
It moves your birth date forward month by month and clamps to the last day of a short month. For example, from 31 January 2020 to 1 March 2021 it counts 1 year, 1 month and 1 day.
How many days old am I?
The Days tile shows the exact number of calendar days from your birth date to the chosen date. Hours, minutes and seconds are shown too, as approximations because they count from midnight to midnight.
When is my next birthday and how many days are left?
The result shows the date and weekday of your next birthday, the number of days to go and a ring that fills as it gets closer.
What if I was born on 29 February?
In years without a 29 February the calculator counts your birthday on 28 February. Some countries use 1 March for legal purposes, so check the rule that applies to you.
What day of the week was I born?
The result shows it, for example Friday. It is calculated from the calendar, so it works for any date from 1900.
Can I calculate age at a past or future date?
Yes. Change the Age at date. Use a past date to find out how old someone was at an event, or a future date to plan, for example the age you will be at retirement.
What is my age on Mars or Jupiter?
Open the Planets and milestones tab. Your days lived are divided by each planet's orbital period, so you are about half your Earth age on Mars and a fraction of a year old on Jupiter.
When will I be 10,000 days old?
The milestone table lists the dates for 1,000, 5,000, 10,000, 15,000, 20,000, 25,000 and 30,000 days, plus one billion seconds. Add your own number of days to get its date.
What is the Korean age shown in the results?
The traditional Korean count, where a person is one at birth and gains a year each 1 January. South Korea moved to the international age system for official purposes in June 2023.
How are generations decided?
The label follows the Pew Research Center birth-year ranges: Baby Boomer 1946 to 1964, Generation X 1965 to 1980, Millennial 1981 to 1996, Generation Z 1997 to 2012 and Generation Alpha from 2013.
Can I compare the ages of two people?
Yes. In the third tab enter two dates of birth and names to see the age difference in years, months, days and total days and who is older.
Is this the age used for official documents?
It uses the standard calendar method, but legal age rules differ by country and purpose. Rely on official documents and local rules for legal decisions.
Is my date of birth stored or sent anywhere?
No. Everything runs in your browser and nothing is saved or uploaded.
Is this age calculator free?
Yes. It is free to use online with no sign-up, and you can copy the results, download a CSV or print a summary.
Can I use it for pets or anniversaries?
Yes. Enter any start date, such as an adoption day, wedding or company founding, to get the elapsed years, months and days.
Sources and further reading
- Pew Research Center, Where Millennials end and Generation Z begins.
- NASA, Planetary fact sheet.
- Time and Date, Leap years.
Sources were consulted in October 2026. Standards and rules can change, so always check the official page for your situation.