Age Calculator

How it works

Your age is the gap between two calendar dates: the day you were born and the day you're checking (today, by default). This calculator reads both dates as plain calendar dates, ignoring time of day and time zone, so the result never depends on where you are or what time you opened the page.

The years/months/days breakdown isn't a simple division of total days by 365.25. Instead, the calculator advances your birth date forward one whole month at a time — clamping the day of month when a target month is too short — until adding one more month would overshoot the reference date. The months it advanced become the years and months of your age; whatever is left over becomes the days. This is what makes "years" mean the same thing a birthday does: you turn a year older exactly on your birthday, not a day early or late because a month in between happened to be short.

People born on February 29 get the same treatment as anyone else, through that same month-clamping rule rather than a special case written just for them. In a non-leap year, a "day 29" target clamps to February 28, so a person born on February 29 is treated as turning a year older on February 28 in a non-leap year, not March 1. That matches the everyday convention used by most calendars and the legal treatment used in several jurisdictions for leap-day birthdays.

Total days is a separate, simpler number: the whole count of days between your birth date and the reference date, with no month or year grouping. It's the number to reach for when you want a round milestone, like knowing the exact day you turn 10,000 days old.

Next birthday is worked out the same way: the calculator finds your birth month and day in the current year, or in the following year if that date has already passed, again clamping February 29 to February 28 in a non-leap year, and reports how many days away it is.

A birth date after the reference date is rejected — there's no meaningful way to compute a negative age. If the two dates are exactly the same, the result is a valid 0 years, 0 months, 0 days, not an error; that's just what "today is the day you were born" looks like.

Examples

A birthday earlier this year. Someone born on June 15, 1990, checked on September 28, 2026, is 36 years, 3 months, and 13 days old — 13,254 total days since birth. Their next birthday, June 15, 2027, is 260 days away.

A February 29 birthday, checked in a non-leap year. Someone born on February 29, 2000, checked on February 28, 2026 (2026 is not a leap year, so February has only 28 days), is shown as exactly 26 years, 0 months, 0 days old. The calculator treats February 28 as their birthday that year rather than waiting for March 1 or jumping straight to the next leap year.

Checking a past or future date instead of today. The "as of" field defaults to today but can be changed to any other date. Entering a reference date of January 1, 2030, for instance, answers "how old will I be on January 1, 2030?" instead of "how old am I right now?" — handy for checking whether you'll meet an age requirement on a specific deadline.

Things to watch for

• A birth date can't be in the future. If the birth date you enter is later than the "as of" date, the calculator shows an error instead of a negative age — there's no meaningful way to be "-2 years old," so this is rejected rather than displayed as a wrong number.
• February 29 birthdays "age" on February 28 in non-leap years. This is a calendar convention used by most everyday age calculators, not a legal ruling that applies identically in every country. If you need a legally exact age-of-majority date for a leap-day birthday in a specific jurisdiction, check that jurisdiction's own rule rather than relying on this calculator alone.
• This is calendar age, not a legal category. The result is the everyday "how old are you" answer — years, months, and days elapsed — not a jurisdiction-specific legal age of majority, retirement eligibility, or similar threshold, which often carry their own rules beyond plain calendar arithmetic.
• Change the "as of" date for past or future age questions, such as "how old was I when X happened" or "how old will I be when Y happens." You don't need today's date to use this tool; any two valid dates work.
• Everything runs in your browser. The birth date you enter is never sent to a server; the calculation happens locally on your device.