Calculating your age (years) is straightforward once you know the Age formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Age Calculator.
What is Age?
The Age calculation tells you your age (years) from a few simple inputs. The figure you are solving for here is the age (years).
The Age formula
This calculation combines several inputs through a multi-step method rather than a single one-line formula. Enter the values below and the calculator resolves each step in order. The inputs it needs are:
- Date of birth — a calendar date. Example: 1990-01-01.
- Age as on — a calendar date. Example: 2026-06-15.
How to calculate it step by step
- Note the date of birth (for example, 1990-01-01).
- Note the age as on (for example, 2026-06-15).
- Apply the formula above to get your age (years).
- Double-check the result with the Age Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Date of birth | 1990-01-01 |
| Age as on | 2026-06-15 |
| Total days | 13,314 |
| Age (years) | 36 |
| Total months | 437 |
| Total weeks | 1,902 |
With date of birth of 1990-01-01 and age as on of 2026-06-15, the age (years) works out to 36.
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Age Calculator does it instantly, for free, with the formula and a worked example built in.
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