Whether you're filling in an official form, checking exam eligibility, or just curious, calculating age from a date of birth comes down to one idea: count the completed years, then the leftover months and days. Here are three ways to do it β from fully manual to fully automatic.
Method 1: By hand (the borrowing method)
Write both dates as day / month / year and subtract column by column, starting with days. When a subtraction goes negative, borrow from the next column β exactly like long subtraction in arithmetic.
Worked example
Date of birth: 14 November 1992 Β· Today: 6 July 2026
| Column | Working | Result |
|---|---|---|
| Days | 6 β 14 = β8 β borrow June's 30 days: 36 β 14 | 22 days |
| Months | (7 β 1) β 11 = β5 β borrow 12: 7 | 7 months |
| Years | (2026 β 1) β 1992 | 33 years |
Age: 33 years, 7 months, 22 days.
Where hand calculation goes wrong
- Borrowing the wrong month length. You borrow from the month before the current one (June's 30 days in the example above, not November's 30 or July's 31).
- Forgetting February. When the previous month is February, borrow 28 days β or 29 in a leap year. The rules are in our Leap Year Guide.
- Off-by-one on the birthday itself. On your birthday, you've completed the year β the new age applies from that day.
Method 2: In Excel or Google Sheets
The DATEDIF function does the whole calculation in one cell. With the date of birth in A1:
Years only: =DATEDIF(A1, TODAY(), "Y")
Years, months, days: =DATEDIF(A1,TODAY(),"Y") & " y, " &
DATEDIF(A1,TODAY(),"YM") & " m, " &
DATEDIF(A1,TODAY(),"MD") & " d"
Total days alive: =TODAY() - A1The unit codes: "Y" = complete years, "YM" = months after subtracting the years, "MD" = days after subtracting years and months. Swap TODAY() for any cell containing a target date to get age at that date.
"MD" unit has documented quirks around end-of-month dates in Excel. For anything critical, verify with a calendar-based tool.Method 3: Online (the 10-second way)
An online age calculator applies the same borrowing method β with every leap year and month length handled β and adds the extras that are tedious by hand: total weeks, days, hours, minutes, and a countdown to the next birthday.
- Open the myagecalc.net age calculator.
- Enter the date of birth.
- Optionally set an "age at" date (it defaults to today).
- Click Calculate β the full breakdown appears instantly.
Everything runs in your browser, so the date of birth is never sent anywhere.
Age in days, months, and years β converting between units
The years-months-days format ("33 years, 7 months, 22 days") is the standard way to state an age, but plenty of situations want a single unit instead: infant milestones in months, medical dosing charts in weeks, milestone celebrations in days. Once you have the breakdown, conversions are simple:
| Want age in⦠| How to get it | For 33y 7m 22d |
|---|---|---|
| Total months | years Γ 12 + months | 403 months |
| Total days | count actual days between the dates (or =TODAY()-A1 in Excel) | β 12,288 days |
| Total weeks | total days Γ· 7, rounded down | β 1,755 weeks |
| Total hours | total days Γ 24 | β 294,912 hours |
One caution on total days: don't estimate it as years Γ 365. Leap days make that figure drift β by more than a week over a 30-year span. Count actual calendar days between the two dates (our age calculator shows the exact total automatically, alongside weeks, hours, and minutes), and see the Leap Year Guide for why the shortcut fails.
Which method should you use?
| Situation | Best method |
|---|---|
| One-off, no device handy | By hand (borrowing method) |
| A whole column of birth dates | Spreadsheet with DATEDIF |
| Exact age with all units, fast | Online calculator |
| Legal/official cutoff dates | Online calculator with a custom "age at" date |
Frequently asked questions
Let the calculator do the borrowing
Exact age in years, months, days, hours, and minutes β from one date input.
Calculate Age Now β