How your age is calculated
The calendar difference between two dates is counted as full years, then full months, then leftover days.
Age = reference date − date of birth, counted in whole years, months and days
- Your age counts every full year from your birth date up to the reference date, not the gap between the two years.
- If your birthday has not arrived yet in the reference year, the year count drops by one.
- The remainder is counted as whole months, then days, using the calendar — so the 15th to the 15th is one month.
- Total days counts every day between the two dates, leap days included, so the figure is exact.
Worked example — Someone born on 14 June 1988 measured on 21 October 2026 is 38 years, 4 months and 7 days old — 14,008 days, or 2,001 weeks — and their next birthday is 236 days away.
Sample ages worked out
| Date of birth | Age at this date | Age | Total days | Total months |
|---|---|---|---|---|
| 1 Jan 2020 | 31 Dec 2026 | 6 years, 11 months, 30 days | 2,556 days | 83 months |
| 1 Jan 2015 | 31 Dec 2026 | 11 years, 11 months, 30 days | 4,382 days | 143 months |
| 1 Jan 2010 | 31 Dec 2026 | 16 years, 11 months, 30 days | 6,208 days | 203 months |
| 1 Jan 2000 | 31 Dec 2026 | 26 years, 11 months, 30 days | 9,861 days | 323 months |
| 1 Jan 1990 | 31 Dec 2026 | 36 years, 11 months, 30 days | 13,513 days | 443 months |
| 1 Jan 1980 | 31 Dec 2026 | 46 years, 11 months, 30 days | 17,166 days | 563 months |
| 29 Feb 2000 | 31 Dec 2026 | 26 years, 10 months, 2 days | 9,802 days | 322 months |
Swipe the table sideways to see the rest.
Ages shown as at 31 December 2026, the cut-off many schools, sports and licence rules use. Put your own dates in the calculator above.
Things to consider
- School, sport and licence cut-offs use a fixed date, so check the age at that date rather than today.
- A baby's age is more useful in months — the total months line gives it directly.
- Someone born on 29 February has their next birthday counted from 1 March in a non-leap year.
- For travel or visa forms, use the age at the date of travel — the second date field lets you check it.
Frequently asked questions
How do I calculate my age?
Count full years from your date of birth to today, then the leftover months and days. If your birthday has not come around yet this year, subtract one from the year count.
Why is my age one year less than the two years suggest?
The gap between two years only counts as a full year once your birthday has passed in the current year. Born in 1990, you are still 35 until your 2026 birthday.
How is a leap-year birthday handled?
A 29 February birthday is counted from 1 March in a non-leap year, so the day count stays correct.
Can I check an age at a past or future date?
Yes. Change the reference date to any date — useful for visa forms, school enrolment and sport age groups.
How are total days counted?
Every day between the two dates is counted, including 29 Februarys, so the figure is exact rather than an estimate.
Results are estimates for general information only, not financial, medical or professional advice.