How your exact age is worked out
The calculator counts whole years first, then whole months, then the days left over. It compares the day and month of your birth with the "age on" date. If that day hasn't come round yet this year, the last year isn't counted. If the day of the month hasn't come yet, the last month isn't counted, and the leftover days are taken from the length of the previous month. This is the same way people normally say their age, and the way official forms ask for it.
Totals in days and weeks are worked out from the exact number of calendar days between the two dates, so leap years are included automatically. Dates are handled in UTC, so clock changes such as British Summer Time can't add or lose an hour and push the result out by a day.
Worked example
Someone born on 20 May 1990 is, on 15 October 2026, 36 years, 4 months and 25 days old. Their 36th birthday was on 20 May 2026. The 20th of the month last fell on 20 September, and 25 days later is 15 October.
Birthdays on 29 February
If you were born on a leap day, the countdown uses 1 March in years that have no 29 February. In UK law a person born on 29 February legally reaches a new age on 1 March in non-leap years.
Uses
Check your age for an application, work out how old a child will be on a school start date, find the day of the week you were born, or count down to a birthday. Everything runs in your browser and no dates are sent anywhere. For gaps between any two dates, try the date calculator.
Frequently asked questions
How do I calculate my exact age?
Count whole years since your birth date, then whole months, then the leftover days. The calculator does this instantly.
How many days old am I?
Enter your date of birth and the result shows total days, weeks and months lived, with leap years included.
What day of the week was I born?
The result shows the weekday for your date of birth.
How to use the Age Calculator
- Pick the date or dates.
- Choose any options (such as excluding weekends).
- Read the result in UK date format.
- Check the bank holiday table below.
Why use this Age Calculator
100% in your browser
Nothing you enter is uploaded or stored.
Instant results
Updates as you type, no waiting.
Mobile friendly
Works on phones, tablets and desktops.
Light & dark mode
Follows your mfaysal.com theme.
Free, no account
No sign-up, no limits, no watermark.
Explained
Formulas, tables and sources on the page.
Age Calculator: chart and reference data
Source: Gregorian calendar
| Date | Holiday |
|---|---|
| Thu 01 Jan | New Year's Day |
| Fri 03 Apr | Good Friday |
| Mon 06 Apr | Easter Monday |
| Mon 04 May | Early May bank holiday |
| Mon 25 May | Spring bank holiday |
| Mon 31 Aug | Summer bank holiday |
| Fri 25 Dec | Christmas Day |
| Mon 28 Dec | Boxing Day (substitute day) |
Age Calculator compared with the alternatives
| Option | Bank holidays | Leap years | Effort |
|---|---|---|---|
| This tool | UK built in | Automatic | Seconds |
| Paper calendar | Manual | Manual | Minutes |
| Spreadsheet NETWORKDAYS | You list them | Automatic | Formula setup |
Who uses it in the UK
- Planning annual leave and notice periods
- Project deadlines and invoices
- Birthdays, anniversaries and ages
- Contracts that count working days
More questions
Does it use UK date format?
Yes. Dates are shown day-month-year, the order used in the UK, to avoid US-style confusion such as 03/04 meaning 3 April vs 4 March.
How are leap years handled?
The Gregorian rule is used: years divisible by 4 are leap years, except centuries not divisible by 400. 2028 is the next leap year.
Are Scottish and Northern Irish bank holidays different?
Yes. Scotland has 9 (including 2 January and St Andrew's Day) and Northern Ireland has 10 (including St Patrick's Day and 12 July).
Do clocks changing affect the result?
Day counts are based on calendar dates, so the British Summer Time change in March and October does not change the number of days.
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Related free tools
Sources
- Time and Date – Age calculator method (reference)
- UK Family Law Reform Act 1969, s.9 (time a person reaches an age)
Note: This free tool runs entirely in your browser. No data is sent or stored. Results are for information only.