About the Age Calculator
"How old are you?" usually has a simple answer, but many situations need more precision: forms that ask for age in years and months, school entry cut-offs, sports age groups, visa and pension rules, medical dosing for children, or simply curiosity about how many days you have been alive. An exact age is also surprisingly fiddly to work out by hand, because months have different lengths and leap years add an extra day every four years.
This age calculator finds your exact age in years, months and days from your date of birth. It also gives your age as totals in months, weeks, days and hours, the weekday you were born, and a countdown to your next birthday. You can calculate age on today's date or on any other date, past or future.
How to Use the Age Calculator
Enter your date of birth.
Optionally, enter the date to calculate the age on. Leave it blank to use today.
Your age and the extra details appear below.
How Exact Age Is Calculated
1. Count the whole months from the birth date to the target date
2. Split them into years and months
3. Count the days from the last monthly anniversary to the target date
Anniversaries on the 29th, 30th or 31st move to the last day of shorter months.This matches the way people normally state their age and the way most official forms count it: you become a year older on your birthday, not after an average year of 365.25 days.
Step-by-Step Example
Born 15 May 1990, age on 29 September 2026.
Whole months: from May 1990 to September 2026 = 436 months
(15 September 2026 is the last monthly anniversary)
Years: 436 ÷ 12 = 36 years and 4 months
Days: 15 September to 29 September = 14 days
Age: 36 years, 4 months, 14 days
Total: 13,286 days = 1,898 weeks exactly = about 318,864 hoursThe person was born on a Tuesday. Their next birthday is Saturday 15 May 2027, in 228 days, when they turn 37.
Birthdays on 29 February
People born on 29 February — about 1 in 1,461 — have a true birthday only in leap years. In other years this calculator treats 28 February as the birthday, so someone born on 29 February 2000 is shown as exactly 25 years old on 28 February 2025. Laws differ: in England and Wales, for example, a person born on 29 February legally reaches a new age on 1 March in common years, while other places use 28 February. If the exact legal date matters, check the rules that apply to you.
Month-End Birthdays
A similar issue affects anyone born on the 29th, 30th or 31st of a month when counting months. Someone born on 31 January has a one-month anniversary on 28 or 29 February, because February has no 31st. The calculator uses the last day of the shorter month, so a baby born on 31 January 2000 is exactly 1 month old on 29 February 2000 and 1 month and 1 day old on 1 March.
Age in Other Units
Totals in days, weeks and hours are popular milestones. Many people celebrate turning 10,000 days old, which happens at about 27 years and 4 months, and a billion seconds comes at about 31 years and 8 months. The hours figure assumes a whole number of days, counting from midnight on the birth date, so it is approximate if you know your time of birth.
Why Age Calculations Matter
Exact ages decide real outcomes. Schools admit children who have reached a certain age by a cut-off date; youth sports leagues group players by age on a set day; insurance premiums, retirement benefits and legal rights often start at a precise age. For babies and toddlers, doctors track development in months and weeks, and paediatric growth charts plot measurements against exact age. Using the "age on" date lets you check eligibility for any cut-off.
Age Around the World
Most countries count age from zero at birth and add a year on each birthday, which is what this calculator does. Some East Asian traditions have counted differently: in the traditional Korean system a baby was one year old at birth and everyone gained a year on New Year's Day, so a person could be up to two years "older" than their international age. South Korea standardised on international age for legal purposes in 2023.
Understanding Your Result
The headline is your age in years, months and days.
The in other units line gives your age as months, weeks, days and hours.
The born on line gives the weekday and full date of birth.
The next birthday line gives the date and the days to go.
The calculated on line confirms the date used.
When Should You Use This Calculator?
Use it to fill in forms that ask for exact age.
Use it to check age cut-offs for school, sport, visas or pensions.
Use it to find how many days, weeks or hours old you are.
Use it to work out someone's age on a past or future date.
Common Mistakes
Dividing days by 365. Leap years make this drift; count calendar years instead.
Forgetting the birthday has not yet come this year. Subtracting years alone can overstate age by one.
Using the wrong reference date. Age cut-offs often use a fixed date, not today.
Assuming everyone treats 29 February the same way. Legal rules differ.
Mixing up day and month order. Enter dates in the year-month-day format shown.
Rounding a baby's age to whole years. For young children, months and weeks matter, so use the full years-months-days result.