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Age Calculator

Work out an exact age in years, months, and days from a birthdate, with a countdown to the next birthday.

Calculated in your browser. Nothing is uploaded.

Defaults to today. Change it to measure age on any date.

Enter a date of birth to calculate the age.

How to calculate age from a date of birth

  1. Enter the date of birth

    Pick the birthdate in the first field. The age appears as soon as the date is valid; there is no button to press.

  2. Adjust the as-of date

    The second field defaults to today. Change it to find the age on any past or future date instead.

  3. Read the results

    The exact age shows in years, months, and days, with totals in months, weeks, days, and hours and a next-birthday countdown below.

  4. Copy the summary

    Click Copy age summary to place the age and the birthday countdown on your clipboard.

Why use this tool

Exact age in calendar units

The headline result is whole years, months, and days, computed with month-end clamping so the parts always add back up to the target date.

Four running totals

The same age is also shown as total months, weeks, days, and hours, handy for milestone maths like a 10,000th day.

Next-birthday countdown

A card shows how many days until the next birthday, the weekday it lands on, and the age being turned, including on the day itself.

Age as of any date

Swap the default as-of date of today for any past or future date to answer cutoff and eligibility questions.

Nothing is transmitted

The birthdate is processed by the page alone; it is never uploaded, stored, or logged.

About this tool

This age calculator turns a date of birth into an exact age in calendar years, months, and days, updating the moment both dates are valid. The month arithmetic adds whole months to the birthdate and clamps to the end of shorter months, so the three parts always add back up to the as-of date, including when the span crosses 29 February. Under the headline, the same age is totalled as months, weeks, days, and hours, and a final card counts down to the next birthday, naming the weekday it falls on and the age being turned.

The as-of date defaults to today, but changing it answers a different set of questions: how old a child will be at a school enrolment cutoff, someone's age on the date a form was signed, or how old a person was on a given historical date. The running totals help with milestone maths too, for example spotting when someone passes 10,000 days or 500,000 hours alive.

Everything is computed in the page itself, so the birthdate you type is never transmitted. To measure the gap between two arbitrary dates rather than an age, use the date difference calculator; to add or subtract raw spans of hours and minutes, the duration calculator covers that. One click on Copy age summary puts the whole result on your clipboard.

Frequently asked questions

How does the age calculator work?
Enter a date of birth and the tool counts the full calendar span up to today, then shows it as exact years, months, and days. It also totals the age in weeks, days, and hours and tells you how long until the next birthday.
Can I calculate age as of a specific date?
Yes. By default the age is measured as of today, but you can set a different "as of" date to find someone's age on a past or future day, for example their age at the start of a school year.
How are months and days counted?
The calculator borrows from the previous month when the day of the month has not yet been reached, exactly as people count age in conversation, so the years, months, and days always add back up to the birthdate.
Does it handle leap-year birthdays?
Yes. The browser date engine accounts for leap years and differing month lengths, so a 29 February birthday and any span that crosses it are counted correctly.
Is my birthdate kept private?
Yes. Everything is calculated in your browser. The birthdate you enter is never uploaded, stored, or logged.

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