How do I calculate my age from my birth year?

Subtract your birth year from this year, minus one if your birthday hasn't come yet.

Why am I not 'this year minus birth year' yet?

Because that counts the current year before your birthday has actually arrived.

How do I find an exact age?

Count the full years since birth, then the months and days since your most recent birthday.

How to Calculate Your Age

Published 10/30/2025 · 3 min read · Everyday calculators

Lena Hoffmann — Science & education writer at Allin

Mathematics · Physics

Checked against 2 sources

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In short

To find your age, subtract your birth year from the current year, then subtract one more if your birthday hasn't happened yet this year. Born in March 1990, in July 2026 you are 2026 − 1990 = 36. Born in November 1990, you'd still be 35 until your birthday. Age is completed years, so a birthday only counts once it has passed.

Subtract your birth year from this year, then take one off if your birthday hasn't come yet. Here's the rule, the common mistake, and how to get an exact age.

The basic subtraction

At its simplest, your age is the current year minus your birth year. In 2026, someone born in 1990 is around 36. That single subtraction gets you the answer almost all the time — but 'almost' is the catch, because it silently assumes your birthday for the year has already been and gone. Handle that one detail and the calculation is exact.

Why the birthday check matters

The year difference counts the current year as if it were already complete, which over-counts until your birthday arrives. Born in November 1990, in July 2026 the subtraction gives 36 — but you have not yet turned 36, so you are still 35. The fix is a single check: if this year's birthday is still ahead of you, take one off. After your birthday, the plain subtraction is right.

Completed years, not started ones

Most of the world counts age as completed years: you are 35 right up until the moment you turn 36, even the day before. You don't round up for the year in progress. This is worth knowing because a few counting traditions differ — in some, a newborn starts at one — but the standard everywhere these calculators use is completed years since birth. That is why the birthday, not just the year, decides the number.

Exact age in months and days

Sometimes you need more than whole years — for a baby's milestones, a legal cut-off, or a form that asks for years and months. For that, count the full years since birth, then the months and days from your most recent birthday to today. A baby born on 10 May, seen on 24 July, is two months and 14 days old. It is the same idea as the year calculation, just carried down to the smaller units.

Age calculatorWork out your exact age in years, months and days from your birth date.Try the tool →

Frequently asked questions

How do I calculate my age from my birth year?: Subtract your birth year from this year, minus one if your birthday hasn't come yet.
Why am I not 'this year minus birth year' yet?: Because that counts the current year before your birthday has actually arrived.
How do I find an exact age?: Count the full years since birth, then the months and days since your most recent birthday.

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