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Age calculator

Enter a date of birth to see the exact age today or on any other date, down to the day.

By the Calcist team · Checked against known answers · Updated October 27, 2026

Private: calculated on your device. Nothing you type is sent anywhere.

Next: Counting down to a date instead? Use days between dates, or find a date a number of days away with the date calculator.

How age is calculated

Age is counted the way people say it: whole years first, then whole months, then the days left over.

  1. Count the whole months from the birth date that fit before the end date. Each month lands on the same day number as the birthday.
  2. Split those months into years (12 months each) and months.
  3. Count the days from the last "month birthday" to the end date.
Total days = end date − birth date (calendar days)
Age = whole months ÷ 12 → years and months, then the leftover days

Total days are counted on the calendar (using UTC day numbers), so daylight saving changes never add or lose a day.

Worked example

Someone born on May 15, 1990 is, on October 27, 2026:

  • May 15, 1990 to May 15, 2026 is 36 years.
  • May 15, 2026 to October 15, 2026 is 5 months.
  • October 15 to October 27 is 12 days.

So the age is 36 years, 5 months, 12 days. That's 13,314 days in total, or 1,902 weeks exactly. They were born on a Tuesday, and their next birthday, May 15, 2027, is 200 days away.

Month ends and February 29

When a month doesn't have the birthday's day number, the "month birthday" moves to the last day of that month. Someone born on January 31 is one month older on February 28 (or 29 in a leap year).

People born on February 29 only have a real birthday every four years. There's no single US rule for which day counts in other years, so you can choose:

  • February 28 (the default): the same last-day-of-the-month rule as every other date.
  • March 1: the day after February 28. Some laws, such as the UK's for legal age, use this.

Limitations

  • Some Asian age systems count age differently (for example, the traditional Korean system starts at 1 at birth). This calculator uses the international system, starting at 0.
  • Legal ages for things like retirement benefits can follow their own rules. Social Security, for instance, treats you as reaching an age the day before your birthday, which is why people born on January 1 use the previous year's retirement age. Check the rule that applies to you.
  • Hours are calendar days × 24. They don't add time of day or the hour gained or lost to daylight saving time.
  • Dates before 1582 use the Gregorian calendar extended backwards, not the Julian calendar people used then.

Sources

How we checked this

Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:

  • Born May 15, 1990, on Oct 27, 2026: 36 years, 5 months, 12 days ✓
  • Same dates: 13,314 days in total ✓
  • Leap day birth (Feb 29, 2000) on Feb 28, 2023, Feb 28 rule: 23 years exactly ✓
  • Same with the March 1 rule: 22 years, 11 months, 30 days ✓
  • Born July 20, 1969: a Sunday ✓

Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.

Add this calculator to your website (free)

Paste this code into any web page. The calculator works on your page, resizes itself, has no ads and no tracking, and nothing your visitors type is sent anywhere. More about embedding.

Questions people ask

How do I calculate my exact age?

Count the whole years since your last birthday, then the whole months since your last month birthday, then the days left over. Enter your date of birth above and it's done for you.

How many days old am I?

Subtract your birth date from today's date in calendar days. Someone born May 15, 1990 was 13,314 days old on October 27, 2026.

When does someone born on February 29 turn a year older?

In leap years, on February 29. In other years there's no fixed US rule: many people celebrate on February 28, and some laws use March 1. You can pick either above.

Why is my age in months different from years × 12?

Total months counts every whole month, including the ones since your last birthday. At 36 years and 5 months, that's 36 × 12 + 5 = 437 months.

Does the calculator store my birth date?

No. It runs in your browser and nothing is sent anywhere. If you copy a share link, the date is in the link itself.

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