Age Calculator
Calculate age.
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Why calculating an age is not simple arithmetic
Age looks like subtraction and is not. Months have different lengths, leap years insert a day every four years — except in century years not divisible by 400 — and the conventional way of stating an age counts completed years, so someone born on 1 September is 29 until the day before their thirtieth birthday, not from partway through the year.
Then there are the edge cases that catch software out. People born on 29 February have a birthday in only one year of four, and different jurisdictions treat their legal birthday as 28 February or 1 March. Time zones matter when a birth and the current moment are in different ones. Calculating a precise age means counting whole years, then whole months, then remaining days, respecting the actual length of each month along the way — rather than dividing a day count by 365.25 and rounding.
Why we built this tool
Exact ages are needed for forms, visa and pension applications, insurance quotes, school enrolment cut-offs, medical dosing, and legal thresholds — and for the ordinary curiosity of knowing exactly how old someone is in days.
A date of birth is personal data in every privacy framework, and combined with a name it is one of the strongest identifiers there is. Sending it to a server to perform arithmetic your browser can do instantly is an unnecessary disclosure. Ours calculates entirely in your browser with JavaScript's date handling, so the date is never transmitted, never logged, and never stored. It also answers instantly and works with no connection.
Tips and common mistakes
- Ages count completed years, so a birthday later this year has not happened yet.
- Leap-day birthdays are handled by convention, and jurisdictions differ on which day counts.
- Enter dates in the format the field expects — day and month order is a frequent silent error.
- Use the reference date field to calculate an age as it stood on a past or future date.
Open Age Calculator with a link
Age Calculator can be handed its input by the link that opens it, so the page arrives with the work already done. This is meant for assistants and scripts: if a chatbot, an editor extension, or a command-line agent already holds your content, it can build a link instead of asking you to copy and paste into a box.
The payload rides in the fragment — the part of a URL after the #. Browsers never send the fragment to a server, so anything handed over this way stays on your device exactly as a dropped file would. A link that uses the query string instead is rewritten into the fragment by the page before any analytics or ad script can read the address.
#dob=— date of birth, YYYY-MM-DD#asof=— the date to measure to, YYYY-MM-DD
Example: https://mygadgets.ink/tools/age-calculator/#dob=...&asof=...
Quick start: using Age Calculator
- Enter the date of birth.
- Set the reference date, or leave it as today.
- Read the age in years, months, and days.
- Check the additional totals — days lived, or time until the next birthday.
- Note that leap-day birthdays are handled by convention, which varies between jurisdictions.
For working with machine timestamps rather than calendar dates, use Timestamp Converter.