Age Calculator
Calculate exact age from a date of birth in years, months and days, plus total days lived, next birthday and the weekday you were born.
Calculate your exact age
Enter a date of birth and choose the date you want to calculate age on. Related Calculatorz pages include a notice period and How to work out a notice period end date.
How the age calculator works
The calculator compares your date of birth with the selected calculation date. It counts full years first, then counts the remaining full months, then the leftover calendar days.
That is why exact age is more useful than only subtracting the birth year from the current year. Someone born later in the year has not reached their next full birthday yet.
Age calculation formula
For exact age, the calculation is not just one subtraction. It is a date-difference calculation:
exact age = full years between dates
+ remaining full months
+ remaining daysTotal days old is calculated separately by counting the calendar days between the date of birth and the selected date.
What the result shows
| Output | What it means |
|---|---|
| Exact age | Your age in completed years, remaining months and remaining days. |
| Total days old | The number of calendar days between your birth date and the calculation date. |
| Total weeks | Total days divided into full weeks and remaining days. |
| Next birthday | The next calendar date when the birthday occurs after the selected calculation date. |
| Day of week born | The weekday of the date of birth. |
UK date format warning
UK dates are normally written as day/month/year. For example, 05/06/2026 usually means 5 June 2026 in the UK, but it may be read as 6 May 2026 in a US-style format.
When using any calendar day calculator, the safest approach is to use a date picker or write the month in words.
Leap-year birthdays
If someone was born on 29 February, their birthday only appears on the calendar in leap years. For countdown purposes, people often treat 28 February or 1 March as the observed birthday in non-leap years.
This calculator lets you choose which approach to use for the next birthday countdown. The total days old calculation is unaffected.
Worked examples
Age calculator FAQs
How do I calculate my exact age?
Calculate the difference between your date of birth and the selected date, counting completed years first, then remaining completed months, then remaining days.
Can I calculate age on a past or future date?
Yes. Change the “calculate age on” date to see how old someone was on a past date or will be on a future date.
Does this count the birthday itself?
Yes. On the birthday date, the calculator increases the completed years by one and shows zero days until the next birthday.
Why can total months be approximate?
Calendar months have different lengths. The exact age uses real calendar months, while approximate total months is a summary for quick comparison.