Age Calculator

How to calculate age

1. Enter the complete date of birth using the date field or your browser's calendar.
2. Check Age as of. It starts with your device's local date after the page loads; you can choose another past or future date.
3. Read the years, months and days, along with the comparison date and the month-end rule.
4. Open Calculation details for total elapsed calendar days and the last matched monthly date. Copy the summary if useful; it includes the entered dates.

A clear age calculation

• Calculate age today, on a past date or on a future date from a complete birth date.
• Read one calendar-age answer rather than a dashboard of seconds and decimal years.
• Use a visible rule for month ends and a specific explanation for 29 February births.
• Check total elapsed civil days and the calculation method in expandable details.
• Calculate in your browser without uploading a document or creating an account.

When an age-on-date calculation helps

• Check a personal age today without counting months and days by hand.
• Find the calendar age on a chosen past or future date, such as the date of a family event.
• Understand how a month end or leap-day birth date affects this calculation, without assuming an institution uses the same rule.

Understanding years, months and days

The birth date is age zero. The comparison date must be the same day or later. Identical dates give 0 days; a comparison one day later gives 1 day, with no extra inclusive end day.

This calculator counts monthly dates directly from the original birth day. If that day is missing in a target month, it uses the month's last day. It takes the last such monthly date not after the comparison, groups complete months into years and counts the remaining calendar days.

For a birth date of 31 January 2023, 28 February is one month later under this rule. On 30 March the age is 1 month 30 days, because the next original-day monthly date is 31 March. It does not keep stepping from a previously shortened month.

A 29 February birth date uses 28 February as its matching February day in a non-leap year. From 29 February 2020 to 28 March 2021, the result is 1 year 28 days: the next original-day monthly date is 29 March, not 28 March. In leap year 2024, the fourth matching yearly date is 29 February.

Today comes from your device's local calendar date when the default is set or you press Today. It is a snapshot, not a clock that changes at midnight. Date arithmetic compares Gregorian calendar labels, so daylight-saving changes do not turn a civil day into a fractional day.

Years and months have different lengths, so the result is not total days divided by an average year or month. Different calendar-age conventions can give different month/day parts. The supported range is 0001 through 9999 in the proleptic Gregorian calendar, not a reconstruction of historical local calendars or a legal age decision.

Age calculation examples

Born 10 May 2000, compared with 17 October 2026: 26 years 5 months 7 days, with 9656 elapsed calendar days.

Born 18 October 2000, compared with 17 October 2026: 25 years 11 months 29 days. The next matching yearly date has not been reached.

Born 31 January 2023, compared with 28 February 2023: 1 month and 28 elapsed calendar days. On 30 March the result is 1 month 30 days.

Born 29 February 2020, compared with 28 February 2021: 1 year under this method. Compared with 28 February 2024, the result is 3 years 11 months 30 days because that year's matching date is 29 February.

Born and compared on 17 October 2026: 0 days. The next day is 1 day; the calculator does not add a day for including both endpoints.

What this result does not decide

This is a stated Gregorian calendar-age convention. Legal, school, administrative and cultural age rules can differ, especially for leap-day birthdays; check the rule that applies to your situation.

A complete birth date and comparison date are required. The tool does not estimate from a birth year, infer unknown dates, calculate a birth date from an age or convert another calendar.

Time of birth, timezones, hours, seconds, leap seconds and daylight-saving durations are not part of this calculation. Proleptic Gregorian dates do not establish what calendar a historical record used.

The Today shortcut depends on your device's date settings and does not update by itself. The tool provides no birthday countdown, medical assessment, eligibility advice or guarantee about an external organization's calculation.

Your dates and copied result

This calculator processes the entered dates in your browser and does not add them or the age to the page address or calculator storage. Copy result intentionally puts the dates and age in your clipboard. This is not a claim that the whole site has no analytics or third-party requests.

The calculator does not save your date draft. Clear resets the birth date and uses the device's current date for the comparison when available. Normal language navigation reloads the tool with those defaults, so copy any result you need before leaving.