Age Calculator

This age calculator gives an exact age in years, months and days from a date of birth, measured on today’s date or on any other date you choose. Alongside it you get the totals people are often asked for (whole months, weeks, days and approximate hours), a countdown to the next birthday with the weekday it falls on, the day of the week you were born, and the date you turn 10,000 days old.

It is handy for forms that ask for an age on a certain date, such as school starting ages, visa and pension rules, sports age groups or insurance quotes, and for working out how old a baby is in weeks or how long until a birthday. Set “Age on” to a date in the past or future to answer “how old was I when…” or “how old will they be on…”.

The hard parts are done properly. Month ends follow a clear rule (someone born on 31 January is one month old on the last day of February), people born on 29 February get their birthday on 28 February in other years, and leap years are counted exactly. Dates are handled as calendar days rather than clock time, so time zones and daylight-saving changes never move an answer by a day. Nothing you enter leaves your device.

1. Tap “Date of birth” and pick the date. On iPhone and Android your phone’s own date wheel or calendar opens.
2. Leave “Age on” set to today, or pick another date to see the age on that day. The “Today” button sets it back.
3. Read the exact age in years, months and days, with the totals in months, weeks, days and hours underneath.
4. Scroll a little for the next birthday countdown, the weekday you were born and your 10,000-day date.

• Exact age in years, months and days on today’s date or any date you choose, past or future.
• Totals: whole months, weeks plus leftover days, total days and approximate hours.
• Next birthday: how many days to go, the date, the weekday and which birthday it is (21st, 30th…).
• The day of the week you were born, worked out for any date from the year 1800 to 2200.
• Your 10,000th day: the date and how far away (or how long ago) it is.
• Correct leap-year and month-end rules, including birthdays on 29 February and on the 29th, 30th or 31st.
• Calendar maths with no clock time involved, so results never shift with time zones or daylight saving.
• Uses your device’s built-in date picker, which works well on iPhone, Android and desktop.

• Ages are counted in whole months first, then leftover days. From 31 January to 30 March is 1 month and 30 days, because the one-month mark lands on the last day of February.
• For someone born on 29 February, this tool counts the birthday as 28 February in non-leap years, which is what most people celebrate. Some laws use 1 March instead, so check if it matters for an official form.
• “Total hours” is days × 24 and ignores the one-hour clock changes, so it is marked as approximate. The days, weeks and months are exact.
• Need an age on a past date, such as the start of a school year? Change “Age on” and everything, including the next-birthday countdown, is measured from that date.
• If “Age on” is earlier than the birth date, the tool says so rather than showing a negative age.
• Nothing is saved: close the page and the dates are gone. That keeps a child’s or relative’s birth date private.