Age calculator
Age Calculator in Months and Days
Find an exact age in years, months and days, plus total months, weeks and days and a countdown to the next birthday. Type a birth date and the result appears instantly.
How to use the age calculator
- Pick the date of birth.
- Leave Age as of on today, or set it to any other date to see age on that day.
- Read the age in years, months and days, then check the tiles for the same age expressed in months, weeks and days.
- The next birthday tile counts down the days and shows which weekday it falls on.
Age in months and days, explained
"How old am I in months and days?" has one right answer and several sloppy ones. The right answer counts complete calendar units in order: first the whole years since birth, then the whole months since the most recent birthday, then the days left over. Because a month can be 28, 29, 30, or 31 days long, the leftover day count must use the actual length of the month being crossed. Tools that assume every month is 30 days drift by up to three days a year.
This calculator reports four figures so you can use whichever suits you:
- Years, months, days — the natural way people state age (for example, 5 years, 2 months, 26 days).
- Total months — years × 12 plus the extra months. Pediatric growth charts and developmental milestones are usually tracked this way in the first few years.
- Total weeks — total days ÷ 7, shown as whole weeks plus spare days. Newborn age is very often quoted in weeks.
- Total days — the exact number of days lived, with no rounding.
The next-birthday countdown finds the next time your birth month and day occur on or after the "as of" date. If you were born on February 29, the countdown targets the next real February 29 and, in years without one, treats February 28 as the anniversary.
Every figure is computed from local date components — plain year, month and day integers — so the result never shifts by a day because of your time zone. If you specifically need the assessment format used in speech-language and psychology testing, use our chronological age calculator, which prints the age as years;months;days and explains the manual conventions.
Frequently asked questions
How do you calculate age in months and days?
Count the whole years from birth to the chosen date, then the whole months since the last birthday, then the leftover days. Because months differ in length, the day count uses the real length of the relevant month rather than a flat 30 days.
How many months old am I in total?
Total months is your age in years multiplied by twelve, plus any extra whole months. A person aged 5 years 2 months is 62 months old. The tool shows this next to the full breakdown.
How is the number of weeks old worked out?
It is the total number of days lived divided by seven, shown as complete weeks plus leftover days — the way a baby's age is usually described in the first year.
What happens with a February 29 birthday?
In non-leap years the birthday is treated as February 28, so a year is gained on February 28 and the countdown targets the next February 29 that exists.
Can I calculate age on a past or future date?
Yes. Change the "Age as of" field from today to any date to see how old someone was, or will be, on that day.
DateSpan is a free calendar utility. Results are calendar arithmetic and are provided for general informational purposes only — not medical, legal, or professional advice. For clinical age-in-months figures, confirm against the relevant chart or manual.