Age Calculator
Find your exact age in years, months, days, hours and minutes.
About Age Calculator
Age is computed by subtracting the year, month, and day components separately and borrowing when needed — the same way you'd work it out on paper. This correctly accounts for different month lengths and leap years.
Formula
Age = calendar difference between date of birth and reference date, computed by subtracting year/month/day components and borrowing from the next-larger component when the end value is smaller than the birth value.
- borrowing
- When end-day < birth-day, one month is subtracted and the days of the preceding month are added to the day difference
- totalDays
- Math.floor((end − birth) in milliseconds ÷ 86 400 000)
- totalWeeks
- Math.floor(totalDays ÷ 7)
Worked example
With the default values below, Age Calculator returns Age of 26 years, 9 months, 28 days. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Date of Birth
- 2000-01-01
- Age at Date
Results
- Age
- 26 years, 9 months, 28 days
- Total Months
- 321
- Total Weeks
- 1,399
- Total Days
- 9,798
Step by step
- 1Reference dates
- 2Subtract year, month, and day componentsDay and month components are adjusted with borrowing when the end day or month is smaller than the birth day or month.
- 3Exact age (calendar-aware)= 26 years, 9 months, 28 days
- 4Total elapsed days (millisecond difference ÷ 86 400 000)= 1,399 weeks
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Age Calculator — full guide
When an exact age is required
Visa and passport forms, school admission cut-offs, insurance underwriting, pension eligibility and sports age-group rules all ask for age on a particular date, not age right now. The two fields cover both: Date of Birth (default 2000-01-01) and Age at Date, which is left blank to mean today.
The component-subtraction method
Age is the calendar difference between two dates, worked out the way you would on paper:
- Subtract the day numbers. If the result is negative, borrow the number of days in the month before the reference month and drop the month count by one.
- Subtract the month numbers. If that result is negative, add 12 and drop the year count by one.
- Whatever is left in each column is your years, months and days.
Worked example
Date of Birth 2000-01-01, Age at Date 2026-06-10:
| Column | Birth | Reference | Difference |
|---|---|---|---|
| Day | 1 | 10 | 9 |
| Month | 1 | 6 | 5 |
| Year | 2000 | 2026 | 26 |
Nothing needs borrowing, so the age is 26 years, 5 months, 9 days — 317 total months (26 x 12 + 5), 9,657 total days, and 1,379 full weeks with 4 days over.
Borrowing kicks in when the reference day falls earlier in the month. Take 1998-11-20 to 2026-03-05: 5 − 20 is negative, so borrow February 2026's 28 days to get 13 days and carry one month out of the month column; 3 − 11 − 1 = −9, so add 12 for 3 months and carry a year, leaving 27. The result is 27 years, 3 months, 13 days, which checks out — 2025-11-20 plus three months is 2026-02-20, and 13 days later is 2026-03-05.
Reading the four results
Age is the figure forms want. Total Months (317 here) suits developmental milestones and lease or warranty periods quoted in months. Total Days (9,657) is what day-count milestones need, and Total Weeks is the usual unit for infant and pregnancy tracking.
Limits and edge cases
- Dividing 9,657 days by 365.25 gives 26.44 years. Close, but it is not the calendar answer and can be a day or two out near a birthday.
- Dates only — time of birth is ignored, so the age steps up at midnight.
- A 29 February birth follows the same borrow rule:
2000-02-29to2026-02-28reports 25 years, 11 months, 30 days. Jurisdictions differ on when a leap-day birthday legally falls.
For the plain gap between two dates in days and weeks, use the Date Duration Calculator. The Pregnancy Due Date Calculator handles gestational age, and the Retirement Calculator takes an age as its starting point.
Guides that use this calculator
Frequently Asked Questions
Why not just divide days by 365.25?
That gives an approximation. Proper age uses calendar components so that, for example, someone born on Feb 29 or at month boundaries gets an exact, correct age.
Can I find my age on a future date?
Yes — enter any date in the 'Age at Date' field to see how old you'll be (or were) on that day.
Why does Total Months say 317 when my age shows 26 years 5 months?
They agree: 26 x 12 + 5 = 317. Total Months counts whole months only and discards the leftover 9 days, so it never shows a fraction. If you need those spare days, read them from the Age line or from Total Days, which keeps every one of the 9,657.
What does it report for someone born on 29 February?
The same borrow rule applies. From 2000-02-29 to 2026-02-28 you get 25 years, 11 months, 30 days, because the day column borrows from February. On 2026-03-01 it reads exactly 26 years, 0 months, 0 days. Whether the birthday legally lands on 28 February or 1 March varies by country.
Does the clock time of birth change the result?
No. Both fields take a calendar date with no time component, so a birth at 00:30 and one at 23:45 on the same day give identical output. The age rolls over at midnight rather than at the hour of birth. For hour-level precision you would need a timestamp difference, which this does not do.
What happens if the Age at Date is earlier than the date of birth?
You get a reversed, meaningless span rather than a useful answer, because the method assumes the reference date comes second. Keep the birth date in the first field. To find out how old someone will be later, put the future date in Age at Date — 2000-01-01 against 2030-01-01 gives exactly 30 years.