Age Calculator

Calculate how old you are in years, months and days, and how many days are left until your birthday.

Age in years

July 15, 1990 · October 10, 2026

Plus months

Plus days

Age in months

434

Age in weeks

1,890

Age in days

13,236

Days until the next birthday

278

Next birthday

July 15, 2027

Please note: The result is an estimate and has been rounded. Actual costs and values may differ, and no rights can be derived from this calculation.

How this number is calculated

The blocks use your input. Change a value above and they update with it.

Step 1 · Whole months

year ofAge onOctober 10, 2026 − year ofDate of birthJuly 15, 1990 × Months per year12 + month ofAge onOctober 10, 2026 − month ofDate of birthJuly 15, 1990 − (becauseday ofAge onOctober 10, 2026 less than day ofDate of birthJuly 15, 1990 ) 1 =Whole months434

Step 2 · Age in years

Whole years36 =Age in years36

Step 3 · Plus months

Whole months434 mod Months per year12 =Plus months2

Step 4 · Last whole month ended on

(becauseday ofAge onOctober 10, 2026 less than day ofDate of birthJuly 15, 1990 ) smallest ofFirst day of the monthOctober 1, 2026 − 1 − day ofFirst day of the monthOctober 1, 2026 − 1 + day ofDate of birthJuly 15, 1990 First day of the monthOctober 1, 2026 =Last whole month ended onSeptember 15, 2026

Step 5 · Plus days

Age onOctober 10, 2026 − Last whole month ended onSeptember 15, 2026 =Plus days25

Step 6 · Age in days

Days since birth13,236 =Age in days13,236

Step 7 · Last birthday

date fromyear ofDate of birthJuly 15, 1990 + Whole years36 month ofDate of birthJuly 15, 1990 1 + day ofDate of birthJuly 15, 1990 − 1 =Last birthdayJuly 15, 2026

Step 8 · Days until the next birthday

Days until the birthday278 =Days until the next birthday278

Step 9 · Next birthday

Age onOctober 10, 2026 + Days until the birthday278 =Next birthdayJuly 15, 2027

How the calculation works

Enter a date of birth and the date you want to know the age on. You see the age in years, months and days, also as a total number of months, weeks and days, and how many days are left until the next birthday.

You turn a year older on your birthday. The calculator first counts the whole months since birth: a month is complete when the same day of the month comes around again. Twelve whole months make a year; the months and days left over are added. If you were born on February 29, your birthday counts on March 1 in years without February 29. The total number of days is the difference between the two dates.

Formula

Months = (year − birth year) × 12 + (month − birth month), minus 1 if the day of the birth month has not been reached yet. Age = months ÷ 12, rounded down. Days = date − date of birth. Weeks = days ÷ 7, rounded down.

Assumptions

You turn a year older on the day of your birthday itself.
Born on February 29? In a year without February 29 your birthday counts on March 1.
A month is complete on the same day of the month. If that day does not exist, such as April 31, the 1st of the following month counts.
If today is your birthday, there are 0 days until your birthday.
Only whole days count: the time of birth and time zones are left out.

Example calculations

The button fills in the calculator above, so you can carry on from there.

Age on your first day at work

Age in years
22

Date of birth March 12, 2004 · Age on September 1, 2026

Born on March 12, 2004, first day at work on September 1, 2026.
Age of a baby

Age in years
0

Date of birth March 20, 2026 · Age on October 4, 2026

Born on March 20, 2026: 6 months and 14 days old on October 4.
Born on February 29

Age in years
19

Date of birth February 29, 2008 · Age on March 1, 2027

Born on February 29, 2008: in 2027 the birthday falls on March 1.

Frequently asked questions

How do I calculate my age?

Subtract your year of birth from the current year. If you have not had your birthday yet this year, subtract 1. Born on July 15, 1990? On October 4, 2026, you are 2026 − 1990 = 36, because your birthday has already passed.

How old am I in days?

That is the number of days from your date of birth to today, including every leap day. Someone born on July 15, 1990, is exactly 13,230 days old on October 4, 2026. Enter your own date of birth and the calculator figures it out.

When is my birthday if I was born on February 29?

In a leap year simply on February 29. In other years this calculator uses March 1, because only then has the whole of February 28 passed. Official rules can differ: some countries and organizations use February 28 instead.

How many days until my birthday?

Enter your date of birth and set ‘Age on’ to today's date. The calculator shows how many days are left and on which date your next birthday falls. If today is your birthday, it shows 0.

How do I calculate a baby's age in months?

Count the whole months since birth. A baby born on March 20 is 1 month old on April 20 and 6 months and 14 days old on October 4. The calculator also shows the total number of weeks, which is handy in the first year.

Can I calculate my age on another date?

Yes. Enter any date under ‘Age on’, in the past or in the future. That way you can see how old you were on your wedding day, or how old you will be on your first day at a new job.

Sources and checks

Sources

Leap Years | U.S. Naval Observatory, Astronomical Applications Department (opens in a new tab)aa.usno.navy.mil · accessed October 5, 2026

How we check it

This calculator has 21 fixed checks: 17 calculations with a result that is fixed in advance, and 4 cases of invalid input that must be rejected. They all run automatically every time we publish; if one fails, the calculator does not go live.

See the calculations

Date of birth July 15, 1990 · Age on October 4, 2026 → Age in years 36
Date of birth March 12, 2004 · Age on September 1, 2026 → Age in years 22
Date of birth March 20, 2026 · Age on October 4, 2026 → Age in years 0
Date of birth February 29, 2008 · Age on March 1, 2027 → Age in years 19
Date of birth February 29, 2000 · Age on February 28, 2027 → Age in years 26
Date of birth February 29, 2000 · Age on February 29, 2028 → Age in years 28
Date of birth February 29, 2000 · Age on February 28, 2028 → Age in years 27
Date of birth October 4, 1990 · Age on October 4, 2026 → Age in years 36
Date of birth October 5, 1990 · Age on October 4, 2026 → Age in years 35
Date of birth October 4, 2026 · Age on October 4, 2026 → Age in years 0

Changes

October 5, 2026: Sources added and content reviewed.
October 4, 2026: First version.

Last reviewed: October 5, 2026 · How we build and check our calculators