How Old Am I? Calculate Your Exact Age in Years, Months & Days
Use the Age Calculator below — enter your date of birth (and an optional age-as-of date), then click Calculate to see your exact age.
Leave "Age as of" blank to use today's date. Enter weeks born early to also see your corrected (adjusted) age — used by pediatricians for premature babies.
What Is Chronological Age?
Chronological age is the amount of time that has passed since a person's date of birth, measured in completed years, months, and days. It is the standard definition of age used in school enrollment, legal milestones, medical records, and eligibility rules — and it is the number this age calculator computes. If someone says "how old am I?", the answer is their chronological age.
In psychology and medicine, chronological age is the baseline against which other ages are compared: mental age (how a child's thinking compares to average children of that age), developmental age (skills and milestones), and biological age (how old the body appears). A child's IQ is classically calculated as mental age ÷ chronological age × 100.
Chronological Age vs. Biological Age
Your chronological age is fixed — it moves forward one day at a time from your birthday. Your biological age estimates how old your body acts, based on blood pressure, heart rate, fitness level, and other biomarkers. A 60-year-old who lifts weights and sleeps well may have a biological age of 50, while a sedentary 40-year-old may have a biological age of 52. Chronological age tells you when you were born; biological age tells you how your body is aging.
How to Calculate Your Age by Hand
To calculate chronological age without a calculator, subtract your birth date from the current date column by column:
- Days: If today's day is smaller than your birth day, borrow one month (use the previous month's day count).
- Months: If today's month is smaller than your birth month, borrow one year.
- Years: Subtract the birth year.
Example: Born March 15, 1998; today is August 10, 2026. Days: 10 − 15 is negative, so borrow July's 31 days → 31 + 10 − 15 = 26 days. Months: July (7) − March (3) = 4 months. Years: 2026 − 1998 = 28. Result: 28 years, 4 months, and 26 days. This is exactly what the age calculator above does for any date of birth.
How Many Days, Weeks, and Hours Old Are You?
Beyond years, months, and days, the same birth date can be expressed in other units. Multiply your age by 365.25 (the average year length including leap years) for total days, divide by 7 for weeks, or multiply by 24 for hours. A 28-year-old has lived about 10,227 days (28 × 365.25) — roughly 1,461 weeks, 245,448 hours, and 14.7 million minutes. The calculator shows all of these totals instantly, plus the day of the week you were born and how many days until your next birthday.
What Is Corrected (Adjusted) Age?
Corrected age (also called adjusted age) is the chronological age of a premature baby minus the number of weeks they were born early. A baby born 6 weeks premature who is chronologically 10 months old has a corrected age of 8.5 months. Pediatricians use corrected age until about age 2 to judge growth and developmental milestones, because babies born early are not expected to reach them at the same pace as babies born full term. Enter the weeks born early in the calculator above to see both your chronological age and corrected age.
How to Calculate Age in Excel and Google Sheets
If you keep birth dates in a spreadsheet, use the DATEDIF function with today's date:
=DATEDIF(A1,TODAY(),"Y")— completed years=DATEDIF(A1,TODAY(),"YM")— remaining months=DATEDIF(A1,TODAY(),"MD")— remaining days
The same formula works in Excel and Google Sheets, making it easy to build a workable age calculator for employee rosters, class lists, or membership records.
Why Your Age Matters
- School eligibility: Age cutoffs decide when a child can start kindergarten and which grade year they are placed in.
- Legal milestones: Turning 18 (adulthood), 21 (drinking age in the US), and 65 (Medicare) are all based on chronological age.
- Health measurements: BMI for children uses age percentiles, and calorie needs, heart rate zones, and many lab reference ranges change with age — our BMI Calculator and Calorie Calculator use your age in their results.
- Planning milestones: Pregnancy due dates, retirement planning, and tax decisions all revolve around specific ages — try our Pregnancy Due Date Calculator and Retirement Calculator.
Related Calculators
Looking for a different kind of age calculation?
- Dog Age Calculator — convert dog years to human years by breed size.
- Cat Age Calculator — convert cat years to human years.
- Date & Time Calculator — add or subtract days, weeks, and months from any date.
- Time Duration Calculator — hours and minutes between two clock times.
- Pregnancy Due Date Calculator — gestational age and due date from your last period.
FAQ
Your age is the amount of time that has passed since your date of birth, counted in completed years, months, and days. For example, someone born on March 15, 1998 was 28 years, 4 months, and 26 days old on August 10, 2026. Enter your date of birth in the calculator above to get your exact age.
Chronological age is the amount of time that has passed since a person was born, measured in years, months, and days from their date of birth. It is the standard definition of age used for school enrollment, legal milestones, medical records, and eligibility for benefits. In psychology, it is the age used to compare mental age, developmental age, and other measures of maturation.
Chronological age is simply how many years, months, and days have passed since your birth. Biological age estimates how old your body appears based on biomarkers, fitness, and organ function. Two people of the same chronological age can have very different biological ages — a 60-year-old who exercises and eats well may have a biological age closer to 50, while an unhealthy 40-year-old may have a biological age closer to 55.
Subtract your birth date from today's date. Start with days: if today's day is smaller than your birth day, borrow one month. Then subtract months: if today's month is smaller than your birth month, borrow one year. Finally subtract years. Example: born March 15, 1998, on August 10, 2026: days 10 - 15 is negative, borrow a month (July has 31 days, so 31 + 10 - 15 = 26 days), months 7 - 3 = 4, years 2026 - 1998 = 28. Result: 28 years, 4 months, 26 days.
Multiply your age in years by 365.25 (the average length of a year including leap days), then add the days from your last birthday. For example, a 28-year-old who last had a birthday 4 months ago is about 28 x 365.25 + 120 = 10,347 days old. The calculator above gives your exact total days, weeks, hours, and minutes.
Corrected (adjusted) age is a premature baby's chronological age minus the number of weeks they were born early. A baby born 6 weeks premature who is chronologically 10 months old has a corrected age of 8.5 months. Pediatricians use corrected age until about age 2 to evaluate development, because babies born early are not expected to reach milestones at the same pace as babies born full term. Use the prematurity adjustment field in the calculator above.
Use the DATEDIF function: =DATEDIF(A1,TODAY(),"Y") for years, =DATEDIF(A1,TODAY(),"YM") for months, and =DATEDIF(A1,TODAY(),"MD") for days, where A1 holds the birth date. In Google Sheets, the DATEDIF and YEARFRAC functions work the same way.
If you were born in 2006, you are 19 years old if your birthday has already passed this year, or still 18 until your birthday arrives. For example, a person born in January 2006 was 20 years old by August 2026, while someone born in December 2006 turns 20 in December 2026. The calculator above gives the exact answer for your birthday.
Your age on a specific date is the time between your date of birth and that date, counting only completed years, months, and days. This is useful for test dates, school eligibility cutoffs, insurance applications, and contest entries. Set the "Age as of" date in the calculator above to any past or future date.
For adults, age does not change BMI categories, but it changes how other measurements are interpreted. For children and teens aged 2-20, BMI is compared against CDC percentiles for the same age and gender. Resting heart rate, calorie needs, and hormone levels also shift with age. Enter your age in our BMI Calculator and Calorie Calculator for age-aware results.
Age difference is simply the time between two dates, or between two dates of birth, expressed in years, months, and days. It tells you how much older or younger one person is than another, or how much time has passed between two events. Switch to the Age Difference tab in the calculator above and enter the two dates.
A dog's first year equals about 15 human years, the second year adds about 9 more, and every year after that adds 4-5 human years depending on breed size. Cats are similar: the first year equals about 15 human years and each year after is roughly 4 human years. Use our Dog Age Calculator and Cat Age Calculator for an exact estimate.
Sources: CDC — age-based growth and BMI percentiles for children; American Academy of Pediatrics — corrected age for premature infants; WHO — chronological age as a standard demographic measure. This calculator is for informational purposes only and is not a substitute for professional medical advice.
Free Online Calculators
Age Quick Facts
- Your chronological age is the time since your date of birth.
- One year averages 365.25 days once leap years are counted.
- Corrected age = chronological age − weeks born early.
- The average US life expectancy at birth is about 77 years.
- A 7-year-old dog is roughly 44 human years old.
- A 3-year-old cat is roughly 28 human years old.