# How old am I?

Works out your age today, or on any date, from the year you were born: one number after your birthday, one less before it.

- Page: https://www.acalculator.org/days/how-old-am-i
- JSON spec: https://www.acalculator.org/days/how-old-am-i.json
- Version: 2f58f9bb298a

## Default answer

Example with the default inputs (Year you were born 2000, Age on September 29, 2026) on the example date Tuesday, September 29, 2026: Born in 2000, on September 29, 2026 the age is 25 or 26: 26 if the birthday in 2026 has come, 25 if not.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| year | Year you were born | The year of birth, 1900 to 2100. |
| on | Age on | The date to find the age on. Today, unless you change it. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| ages | Age in years | The age on the date: two numbers, the lower one before that year’s birthday. |
| after | From the birthday on | The age on the date if the birthday in that year has come. |
| before | Before the birthday | The age on the date if the birthday in that year is still to come. |
| detail | Which one | Which age applies when. |

## Method

Age = year of the date − birth year, once the birthday in that year has come; one less before it.

## Assumptions

- Age counts completed years, as in everyday use: you turn 1 on your first birthday.
- Without the month and day of birth, the age on most dates is one of two numbers; on the date’s year the birthday decides which.
- Only the year is known, so in the birth year itself the age shows as 0 even on a date before the birth.
- Someone born on February 29 has a birthday on February 28 or March 1 in other years; either way, the year difference is the same.

## Worked examples

1. year = 2000, on = 2026-09-28 gives after = 26, before = 25, ages = 25 or 26. Source: hand calculation: 2026 − 2000 = 26 after the 2026 birthday, one less before it.
2. year = 2000, on = 2030-01-01 gives after = 30, before = 29. Source: hand calculation: 2030 − 2000 = 30; on January 1 only a January 1 birthday has come.
3. year = 2000, on = 2000-12-31 gives after = 0, ages = 0. Source: hand calculation: 2000 − 2000 = 0.

## FAQ

### How do I work out my age from my birth year?

Subtract your birth year from the current year. If your birthday this year has passed, that is your age; if not, take away 1. Born in 2000: 2026 − 2000 = 26, so 25 or 26.

### Why does it show two ages?

The year alone does not say whether your birthday has come yet this year. The higher age applies from your birthday on, the lower one before it.

### How do I find my exact age?

Use the DOB calculator: from your full date of birth it gives your age in years, months, and days, the total days, and your next birthday.