Working out your exact age sounds simple, but it's easy to be off by a year. Here's the reliable method, the mistake most people make, and how to get your age down to the day.
To do it instantly for any birth date, use the age & date calculator.
The simple method
To calculate your age in years:
- Subtract your birth year from the current year.
- Check whether your birthday has already happened this year.
- If yes, that number is your age. - If no (your birthday is still to come), subtract 1.
Example: Born 10 December 2000, today is 31 May 2026. 2026 − 2000 = 26. But your birthday (10 December) hasn't happened yet in 2026, so subtract 1 → you are 25.
The mistake to avoid
The most common error is just doing current year − birth year and stopping there. That's only correct after your birthday each year. Before your birthday, it overstates your age by one. Always do the birthday check.
How to count your age in days
Age in days is harder by hand because months have different lengths and leap years add a day. The reliable way is to count the actual days between your date of birth and today — which the date calculator does instantly, including leap years.
As a rough guide, one year ≈ 365.25 days, so multiply your age in years by 365.25 for an estimate.
How age is counted in different cultures
In most of the world, you're 0 years old at birth and turn 1 on your first birthday. Some traditional systems count differently — for example, the traditional East Asian age reckoning considered a baby 1 at birth — though most countries now use the international system officially.
Quick answers
How do I calculate my age? Subtract your birth year from the current year, then subtract 1 if your birthday hasn't happened yet this year.
Why is my calculated age sometimes one year too high? Because "current year − birth year" only works after your birthday; before it, subtract one.
How do I find my age in days? Count the actual days between your birth date and today (accounting for leap years) — the date calculator does this for you.
How many days is one year? About 365.25 days on average (365 in a common year, 366 in a leap year).