Find exact age in years, months, days, and hours.
Calculator
ADDITIONAL INFORMATION
Enter your date of birth and this age calculator returns your exact age in years, months, and days — plus your total days lived and the countdown to your next birthday. It takes a couple of seconds and needs no sign-up. Below the calculator you'll find how age is actually worked out, why two calculators can give slightly different answers for the same date, how leap years and 29 February birthdays are handled, and how age counting differs around the world. Whether you're completing a form, tracking a child's age in months, or just curious how many days you've been alive, start with the calculator above.
An age calculator works out how much time has passed between a date of birth and a reference date, usually today. It returns that span in years, months, and days rather than a single rounded number.
You enter a birth date, and optionally a second date if you want your age at some past or future moment. The tool compares the two dates on the Gregorian calendar and reports the elapsed time.
Good age calculators also express the same span in other units — total days, weeks, and hours — and show how long until the next birthday. Because the calculation follows calendar rules rather than simple division, the result matches the age you'd state on a form or application.
Age is calculated by comparing calendar dates, not by dividing days by 365. The method works from the largest unit to the smallest:
Age increments on the birthday itself, not at any point during the birth year. That is why your age in whole years stays the same for twelve months and then jumps by one.
Why not just divide by 365? Calendar years are not all 365 days. Leap years add a day, and months range from 28 to 31 days. Dividing total days by 365 drifts over time; calendar arithmetic avoids that drift.
If two calculators give you different answers, the cause is almost always how they handle uneven month lengths — and there is no single universal convention.
Consider 31 January plus one month. February has no 31st, so the result must be either 28 February, clamping to the end of the month, or 3 March, rolling over into the next month. Both are defensible. Different software libraries make different choices, and that choice can change the days figure.
The same ambiguity appears whenever a birth date falls on the 29th, 30th, or 31st and the reference date lands in a shorter month. In practice, the discrepancy is usually one or two days and never affects your age in whole years — the number you would write on a form.
If a result matters legally or medically, treat any calculator as an estimate and confirm it against the official record.
A leap year adds 29 February to keep the calendar aligned with the solar year. A year is a leap year if it is divisible by 4, except century years, which must be divisible by 400. So 2000 was a leap year, 1900 was not, and 2024 was.
People born on 29 February — sometimes called leaplings — have a birth date that appears only once every four years. Their age still advances every year; the question is which day it advances on in a common year.
Most calculators use one convention without explaining it, which is why a leapling's age in days can vary between tools. In leap years the ambiguity disappears because the actual date exists. None of this affects age in whole years: someone born on 29 February 2000 is 26 in 2026 regardless of which convention applies.
The same elapsed time can be expressed in whatever unit suits your purpose. These values are approximate for a 35-year-old because the exact total depends on the leap days in the span.
| Unit | Approximate value | Typically used for |
|---|---|---|
| Years | 35 | Forms and official records |
| Months | ~420 | Infant and toddler development |
| Weeks | ~1,826 | Pregnancy and early infancy |
| Days | ~12,784 | Milestones and curiosity |
| Hours | ~306,800 | Novelty and milestones |
Months matter most for young children. Growth charts, vaccination schedules, and developmental milestones are tracked in months because the difference between an 18-month-old and a 24-month-old is substantial. Gestational age measures development from the last menstrual period, while corrected age adjusts a premature baby's age to reflect the original due date. These are clinical measures, so use the figures your healthcare provider gives you.
Most of the world uses international age: you are zero at birth and gain a year on each birthday. This is what an age calculator returns by default, but it is not the only system people have used.
Traditional East Asian age reckoning starts a newborn at one year old, and everyone advances a year together at the lunar new year rather than on individual birthdays. Under this system, a baby born days before the new year could be counted as two years old within a week of being born.
South Korea used a version commonly called Korean age — starting at one and adding a year every 1 January — alongside international age for decades. In June 2023, South Korea standardised on international age for legal and administrative purposes, making most Koreans one or two years younger on paper. Traditional counting still appears in conversation, but official documents use international age.
China, Japan, and Vietnam historically used similar systems. All have adopted international age officially, although traditional reckoning survives in cultural and ceremonial contexts. For visas, employment, medical records, and other official purposes, international age is the standard.
If you are working with dates, these tools cover the neighbouring questions:
Enter your date of birth above for your exact age in years, months, and days, plus your total days lived and detailed breakdown. If you need the span between two other dates, use the Date Calculator; for an upcoming event, use the Countdown Timer. Bookmark this page — forms ask for exact age more often than you would expect.
Need to cite this calculator for academic papers, engineering notes, or school assignments? Use the reference below: