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SPCXTools

Age Calculator

Find your exact age in years, months and days — and how many days until your next birthday.

Runs locally — files never leave your device

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How to use Age Calculator

  1. 1Enter the date of birth.
  2. 2Leave Age on set to today, or pick another date to find someone's age on a specific day.
  3. 3Read the exact age in years, months and days, plus totals in months, weeks, days and hours.
  4. 4See how many days remain until the next birthday and which day of the week the person was born.

Calculate your exact age

How old are you, exactly? This age calculator works out the precise time between a date of birth and today — or any other date — in years, months and days. It also converts the result into total months, weeks, days and hours, counts down to the next birthday, and tells you the weekday you were born. Everything is calculated in your browser, so birth dates are never sent anywhere.

What you get

  • Exact age in completed years, months and days.
  • Totals in months, weeks, days and hours — fun for milestones like your 10,000th day.
  • Next birthday countdown, including the age you will turn.
  • Day of the week you were born.
  • Any reference date, past or future, not just today.

Practical uses

Forms and eligibility. Check whether someone meets an age requirement on a specific date — school enrolment cut-offs, sports age groups, retirement, insurance, or the minimum age for a licence.

Historical and family research. Find how old an ancestor was at marriage, emigration or death by entering both dates.

Milestones and celebrations. Discover when you turn 10,000 days old (about 27 years and 4 months) or 1,000 weeks old (about 19 years and 2 months), or plan a party around the next birthday.

Pets and projects. The same calculation works for the age of a pet, a company, a building or a relationship.

How the calculation works

Age is not simply the number of days divided by 365, because months have different lengths and leap years add an extra day. The calculator instead compares the calendar dates directly:

  1. Count how many whole months fit between the birth date and the reference date, and express them as years and months.
  2. Step forward from the birth date by that many months. If the target month is shorter than the birth day (for example, 31 January plus one month), use the last day of that month.
  3. Count the remaining days from there to the reference date.

For example, from 31 January to 1 March is 1 month (to 28 or 29 February) and 1 day, in both leap and non-leap years.

To count the days between any two dates — not just birthdays — use the Date Difference Calculator. To convert a moment in time to a Unix timestamp, try the Timestamp Converter.

Frequently asked questions

How is age calculated?
The calculator counts complete years first, then complete months, then the remaining days — the same way people normally state their age. When a month is shorter than the birth day (such as 31 January to February), it uses the last day of that month, so the result is exact across months of different lengths and leap years.
How are people born on 29 February handled?
In years that are not leap years, the calculator treats 28 February as the birthday, so the age increases on that day. Legal conventions differ between countries — some, such as the UK for many purposes, use 1 March instead.
Can I calculate age on a past or future date?
Yes. Change the Age on date to find how old someone was on a past event, or will be on a future one, such as the start of school or a retirement date.
Why is my age in days different on another site?
Some calculators include the end date as an extra day or use the current time of day. This tool counts calendar days between the two dates, not including the end date, which is the standard way to state age in days.
Does East Asian age reckoning differ?
Yes. Traditional Korean and Chinese age counting starts at one at birth and adds a year at New Year. This calculator uses the international system, in which a newborn is zero years old. South Korea officially adopted the international system in 2023.
Is my birth date stored?
No. The calculation runs entirely in your browser.

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