In this article
Your age is the time that has passed since your date of birth, normally written in completed years. Forms for exams, jobs and insurance often want more: years, months and days as on a given date. Calendar months have different lengths, so the result is not just a subtraction of numbers, and a small mistake can decide whether you meet an age limit.
How exact age is worked out
The method is the same one you would use on paper. Count the full years, then the full months left over, then the remaining days. When the day of the month in the target date is smaller than the birth day, you cannot count the last month in full, so you count one month fewer and take the days from the last complete month.
- 1Count the full years1 Jan 2000 to 1 Jan 2026 is **26 years**.
- 2Count the full months1 Jan 2026 to 1 Oct 2026 is **9 months**.
- 3Count the leftover days1 Oct to 9 Oct is **8 days**.
- 4Write the result**26 years, 9 months, 8 days**.
The tool shows more than that: total days, total weeks, total months, total hours, days to the next birthday and the weekday you were born on.
When the days do not line up
The tricky case is a target date with a smaller day number than the birth date. Take a birth date of 25 March 1995 and the date 9 October 2026. From 25 March 1995 to 25 September 2026 is 31 years and 6 months. Then 25 September to 9 October is 14 days, which is the month's remaining days and not 9 − 25.
| Born on | Age on 9 October 2026 | Total days |
|---|---|---|
| 1 January 2000 | 26 years, 9 months, 8 days | 9,778 |
| 25 March 1995 | 31 years, 6 months, 14 days | 11,521 |
| 9 October 2000 | 26 years, 0 months, 0 days (birthday today) | 9,496 |
A person whose birthday is on the comparison date counts the full year, and the next-birthday figure shows 'Today'.
How many days have you lived?
Total days is the difference between the two dates. A year has 365 days, or 366 in a leap year, so the average is about 365.2425. That is why a person of 30 has lived about 10,957 days and not exactly 30 × 365 = 10,950.
Values are rounded and can differ by a day or two depending on how many leap days fall in your own life. The tool counts the exact days between the two dates.
Total hours is days times 24, so it does not count the part of today that has passed.
Age as on a cut-off date
Exam and job notices usually say 'age as on 1 January 2027' or 'as on the last date of application'. Use that date, not today's. The calculator has a second field for the comparison date. Leave it empty for today, or enter the notice date.
- One day short on the cut-off date
- Does not meet the minimum age
- Birthday falls the day after the cut-off
- Turns 18 on the cut-off date
- Meets the minimum age
- Check how the notice counts the exact day
A single day can decide eligibility. Always check the exact rule: some notices say 'completed 18 years' and others say 'not below 18 years'.
Born on 29 February
A leap-day birthday exists only in leap years. In other years people usually celebrate on 28 February or 1 March, and the law in different countries treats the legal birthday differently. This tool treats the birthday in a non-leap year as 1 March, so a person born on 29 February 2004 has 143 days to the next birthday on 9 October 2026, because that birthday falls on 1 March 2027.
A person born on 29 February 2004 has had only five actual 29 February birthdays by 2026, but is 22 years old in calendar terms.
Other ways of counting age
- Completed years is the standard in most of the world: you are 26 until you reach your next birthday.
- East Asian age reckoning traditionally counted a person as one year old at birth. South Korea moved to the international system for most legal and official purposes in June 2023.
- Age last birthday is used by many insurers and is the same as completed years.
- Age nearest birthday is used by some life insurers and rounds to the closest year.
A quick checklist for age on a form
- Find the date the form asks about. It may be today, the last date to apply or a fixed cut-off.
- Enter your date of birth exactly as on your certificate.
- Use the same date in the second field if the age is as on a cut-off.
- Write the age the way the form asks: years only, or years, months and days.
- Keep the supporting document ready. The calculator is a check, and your certificate is the proof.
Questions people ask
How do I calculate my exact age in years, months and days?
Count the full years from your date of birth, then the full months, then the remaining days. If the day of the month in the target date is smaller than your birth day, count one fewer month and take the leftover days from the last full month.
How many days old am I?
Enter your date of birth in the Age Calculator. It subtracts the two dates to give the exact total days, and also shows weeks, months and hours. Someone born on 1 January 2000 is 9,778 days old on 9 October 2026.
How do I calculate age as on a particular date?
Enter your date of birth and also the cut-off date in the second field. Leave the second field empty if you want your age as on today.
When is my next birthday?
The tool shows the number of days to your next birthday. If your birthday is today it says Today. For 1 January 2000 on 9 October 2026, the next birthday is 84 days away.
How are leap years treated?
The calculation uses real calendar dates, so every leap day is counted in the total days. For a 29 February birthday, the next birthday in a non-leap year is counted as 1 March.
Is the result accepted as proof of age?
No. The Age Calculator is a quick check of arithmetic. Official proof of age comes from your birth certificate, school certificate or other document that the form accepts.