Age Calculator Calculators
Exact age in years, months, days — and every other unit going.
Age Calculator is a free online tool that exact age in years, months, days — and every other unit going. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Calculators
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- 2
- Works offline
- Yes, after the first visit
About Age Calculator
Age Calculator is one of 46 calculators tools on DuckyTools, and like all of them it runs entirely inside this page. Exact age in years, months, days — and every other unit going.
How to use it
- Enter date of birth and age at this date.
- Results update the moment anything changes.
The 2 settings
| Setting | What it does | Default |
|---|---|---|
| Date of birth | Free text. | — |
| Age at this date | Defaults to today. | — |
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
| Controls | Date of birth, Age at this date |
Questions
How are months counted?
By calendar, not by a fixed number of days. From 31 January to 28 February is one month, because the day-of-month has been reached as closely as that month allows.
What about leap-day birthdays?
A 29 February birthday is treated as falling on 1 March in non-leap years, which is the convention in most legal systems for reaching a given age.
Is the arithmetic exact?
It uses double-precision floating point — about 15 significant figures, far more than the inputs justify. Displayed rounding is cosmetic; the underlying numbers are not rounded between steps, so chained results do not drift.