Age calculator by date of birth

How old am I? Calculate your age by date of birth

Pick the date of birth and the age appears right away, as of today. Change the second date to get the age on any past or future date, for example how old you will be in 2030 or how old someone was at an event. The calculator shows:

• your exact age in years, months and days, and your age in months, weeks, days and hours;
• your next birthday, with its day of the week and how many days are left, plus the day of the week you were born;
• your next 1,000-day milestone: 10,000 days is a little over 27 years and 4 months;
• the years;months notation used on test reports, and your age in decimal years.

Two more tabs work out the age difference between two people and a birth year from an age. It is free, with no sign-up, and nothing is sent: everything is calculated in your browser.

How exact age is calculated

First, count the full years since birth: that is the age people usually give, and it goes up on each birthday. Then count the full months since the last birthday, from date to date, and finally the days left over. For someone born on June 15, 1990, on November 3, 2026:

1. the last birthday was June 15, 2026: 36 years;
2. from June 15 to October 15, 2026: 4 months;
3. from October 15 to November 3: 19 days.

The exact age is 36 years, 4 months and 19 days, or 13,290 days lived. When the birth day does not exist in the final month, the month ends on its last day: one month after January 31 is February 28, or February 29 in a leap year.

Age by birth year

To work it out in your head, subtract the birth year from the current year, then take away 1 more if the birthday has not happened yet this year. The table shows the age reached on the birthday:

Before the birthday, the age is one year lower: someone born in 1990 is 35 until their 2026 birthday, then 36.

Baby and child age in months and weeks

Up to age 2, the calculator shows the age in months, the way people talk about little ones: “18 months” rather than “1 and a half”. Under one month, it shows days. Weeks are given too, which helps in the first months. A baby born on May 3, 2026 is 6 months old on November 3, 2026, or 26 weeks and 2 days.

Chronological age calculator for testing

Psychologists, speech-language pathologists and teachers record a child’s chronological age on the day of testing, usually as years;months: 7;3 means 7 years and 3 months. The calculator shows it in the last card, along with the age in decimal years. Tests do not all treat the leftover days the same way: some round to the nearest month, others do not. Follow the rule in the test manual to pick the right age band.

Age difference calculator

In the Age difference tab, enter two dates of birth: the tool tells you who is older and gives the exact age gap in years, months and days, in weeks and in days, with each person’s age today. Between March 12, 1988 and September 30, 1992, the gap is 4 years, 6 months and 18 days, or 1,663 days.

Find a birth year from an age

An age alone does not give a birth year: it depends on when the birthday falls. The Birth year tab shows both possible years and the exact dates. On November 3, 2026, a 30-year-old was born between November 4, 1995 and November 3, 1996: in 1996 if their birthday falls between January 1 and November 3, in 1995 otherwise.

Born on February 29: when is the birthday?

February 29 only exists in leap years. In other years, the calculator counts the birthday on February 28, like most date-to-date calculations. Many people born on February 29 celebrate on that day, others on March 1, and laws that set a legal age pick one date or the other depending on the country.

More free tools

• the days between dates calculator also counts business days and adds days to a date;
• the week number tool gives the current week and every week of the year;
• the Roman numeral converter writes a date of birth in Roman numerals.