Age Calculator
Enter your date of birth to find your exact age in years, months, and days. Also shows total days and weeks lived, and when your next birthday falls.
How Age Calculator works
How exact age is calculated
Age is calculated by counting complete years, then complete months, then remaining days. A year is complete if the current month and day have both passed the birth month and day. If the current day is before the birth day in the current month, the month count is reduced and remaining days are calculated relative to the number of days in the previous month.
Leap years and February 29 birthdays
People born on 29 February (a leap day) have a legal birthday on 28 February in non-leap years under UK law. This calculator uses the Gregorian calendar rules for day counting, where February 29 exists only in years divisible by 4 (with corrections for centuries). The total days count is always accurate regardless of leap years, as it measures the raw elapsed milliseconds.
Total days and weeks
The total days lived is the exact number of calendar days from the date of birth to the reference date, calculated from the underlying timestamps. This count includes the day of birth but not the reference date. Total weeks is derived by dividing total days by 7. These figures are useful for milestone calculations — for example, finding the 10,000th day alive.
Next birthday
The next birthday is the first future occurrence of the birth month and day at or after the reference date. Days until the next birthday counts the number of calendar days remaining. This is useful for planning ahead or calculating the age someone will be at a future event.
Frequently asked questions
How do I calculate my exact age?
Subtract your birth year from the current year to get years, then adjust based on whether your birth month and day have occurred yet this year. For exact months and days, count forward from your birthday to today. This calculator does all the arithmetic automatically.
What is my age in days?
Enter your date of birth in the calculator and click Calculate. The result includes your total days lived. As a rough estimate, multiply your age in years by 365.25 (accounting for leap years) to get approximate total days.
When is my 10,000th day alive?
Enter your date of birth and the calculator shows your total days lived. To find your 10,000th day, count 10,000 days forward from your birth date. A rough way to estimate: divide 10,000 by 365.25 ≈ 27.38 years, so your 10,000th day falls roughly at age 27 years and 5 months.
How is age calculated for legal purposes?
In English law, age is calculated in complete years. You reach a new year of age on your birthday. For people born on 29 February, the birthday in non-leap years is treated as 28 February for most legal purposes under the Interpretation Act 1978.
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