Age Calculator

What this age calculator does

This English-language age calculator computes your exact age in years, months, and days from any birthdate — not just today. You can set a custom reference date to find your age at a contract signing, a school enrollment cutoff, or a retirement milestone. Beyond the headline figure, the tool shows total days lived, total weeks, total months, the day of the week you were born, and a countdown to your next birthday. All math runs entirely in your browser: 100% client-side — your data never leaves your browser. No uploads, no tracking, no server logs. For projects that work with epoch-based timestamps, you may also find the [Unix timestamp converter](/en/timestamp-converter/) useful alongside this tool.

Features

• Exact age breakdown. Returns age as years + remaining months + remaining days, not just a rounded year count.
• Configurable reference date. Change the reference date to compute age at any point in time — past or future — useful for legal eligibility checks and contract dates.
• Days, weeks, and months lived. Shows the full cumulative counts so you can answer trivia questions or fill out forms that ask for age in months.
• Birthday countdown. Calculates how many days remain until your next birthday, accounting for leap years correctly.
• Day of the week you were born. Tells you whether you arrived on a Monday, a Saturday, or any other day — a surprisingly popular fact to look up.
• Leap-day support. Handles Feb 29 birthdays gracefully; in non-leap years the tool follows the convention used by most jurisdictions (Feb 28 or Mar 1 depending on context).

How to use the age calculator

Fill in two fields and the result updates instantly. No button to click.

1. Enter your birth date. Type or pick a date in the Birth date field. The tool accepts standard date input in your browser's locale format, which internally maps to ISO 8601 — the date format ranked most preferred by developers in the Stack Overflow Developer Survey 2024.
2. Set the reference date. The Reference date field defaults to today. Click 'Use today' to reset it, or type any past or future date to compute age at that specific moment — for example, the date a New York lease begins or a Seattle school year starts.
3. Read the results. Age appears instantly as years / months / days. Below it you'll see days lived, weeks lived, months lived, days to your next birthday, and the weekday you were born.
4. Use the result in code. If you need the same calculation programmatically, a one-liner covers most cases: in JavaScript, Math.floor((Date.now() - dob) / (365.25*86400000)) gives approximate age in years; in Python, from datetime import date; (date.today() - dob).days // 365 does the same. For databases, DATE_PART('year', AGE(birthdate)) works in PostgreSQL.

Common use cases

• School enrollment eligibility. Many districts use a fixed cutoff date (e.g. September 1) to determine whether a child is old enough to start kindergarten. Set the reference date to the cutoff and enter the child's birthdate to get an instant answer.
• Legal and contract age verification. Verify that a signatory meets a minimum age requirement on the exact date a contract is executed. This is common for insurance applications, lease agreements, and financial accounts.
• Retirement and pension planning. Compute how old you will be on a target retirement date to check whether you meet age thresholds for Social Security, pension schemes, or early-withdrawal rules.
• Medical and wellness forms. Many intake forms ask for age in years and months rather than just a birth year. The tool produces that breakdown directly so you can copy it without mental math.
• Personal trivia and records. Find out the day of the week you were born, how many days you have lived, or how close your next birthday is — details that come up in milestone celebrations and family stories.

Frequently asked questions