Age calculator
Calculate age, total elapsed time, next birthday and weekday of birth.
How to use
Enter a date of birth and the calculator shows the age in completed years, the total time lived, given separately in days, in hours and in minutes, the date of the next birthday and the day of the week the person was born. Everything is measured up to the current date and time on your device.
Completed years are counted the way people count birthdays: the difference between the two years, minus one if this year's birthday has not arrived yet. Someone born on 3 October 1990 is still 35 on 2 October 2026 and turns 36 the next day. Dividing the days lived by 365 or 365.25 gets this wrong around birthdays, because leap days do not fall evenly: one every four years, but not in 1900 or 2100.
The totals count from midnight at the start of the birth date, local time, to now. They are whole days, hours and minutes, rounded down, so the day count goes up around midnight local time, not at the hour of birth (an hour off when daylight saving time differs between the two dates).
People born on 29 February have a real birthday only in leap years. In other years this calculator counts the birthday on 1 March, so the age changes on 1 March and the next birthday shows that date. Laws and organisations do not all agree on this; some use 28 February instead, so check the rule that applies when an age has legal consequences.
A date in the future is rejected. The date of birth stays on your device; nothing is sent to nTools.
Example
1990-03-15On 2 October 2026: 36 years old, 13,350 days lived, next birthday 15 March 2027, born on a Thursday.1990-10-03On 2 October 2026: still 35, because the birthday is the next day.2000-02-29On 2 October 2026: 26 years old, 9,712 days lived, born on a Tuesday. 2027 is not a leap year, so the next birthday is shown as 1 March 2027.
Frequently asked questions
Why can the result differ by one day from another calculator?
The current date and time zone come from your device. Near midnight, or with the clock or time zone set wrongly, the date can be a day off. Some tools also count the day of birth itself as day 1; this one counts elapsed days.
How is age calculated for someone born on 29 February?
In years without 29 February the birthday is counted on 1 March. Some countries and organisations use 28 February instead, so the age can change a day earlier there.
Why not divide the number of days by 365?
Because years are not all the same length. Over 36 years about nine leap days build up, so dividing by 365 makes someone appear to turn a year older more than a week before their birthday.
Can I calculate the age on a past or future date?
Not with this tool, which measures up to today. The Time since a date tool measures the gap between any two dates.