How is age calculated?
Age goes up by one on each birthday. A baby is 0 years old until the first birthday. That is the age used on forms, IDs and in law.
For years, months and days, the calculator counts whole years first, then whole months, then the days left over. Someone born on May 20, 1990 is 36 years, 4 months and 29 days old on October 19, 2026. When a month has no matching day, the last day of that month counts instead, so someone born on March 31 is one month older on April 30.
Age in other units
The result also shows the age as a total number of months, weeks and days. Months are handy for babies and toddlers, and the day count tells you when you reach a milestone such as 10,000 days old (about 27 years and 4 months).
Frequently asked questions
When does someone born on February 29 get a year older?
In years without a February 29, this calculator counts February 28 as the birthday. Laws differ: some places, including Taiwan, use February 28, while others such as the UK use March 1. For legal deadlines, check the local rule.
Can I calculate an age on a past or future date?
Yes. Change the “Age on” date, for example to see how old someone was on a wedding day or will be on a future start date.
Why do some people in Taiwan or China say they are a year or two older?
Traditional East Asian age counting starts at 1 at birth and adds a year every new year, not on the birthday. This calculator uses the international way, which goes up on the birthday.