How to use Age Calculator
The age calculator computes the exact age between any two dates — date of birth and a target date (default: today) — in years, months and days. It also shows total days lived, approximate total hours, the day of the week you were born and how many days until your next birthday. The precise breakdown is useful for legal documents, medical records, milestone tracking and general curiosity.
- Enter your date of birth.
- The target date defaults to today — change it to calculate age at any historical or future date.
- Read your age in years, months and days, plus total days and hours.
- Check the day of birth and days until next birthday.
Your data never leaves your device — 100% private processing.
How age is calculated precisely
Age in years is the number of complete Gregorian calendar years elapsed. Months count completed months after the last birthday year. Days count the remaining days after whole months. This calendar arithmetic means someone born on February 29 (leap day) has a birthday only on actual February 29 in leap years — other years the birthday is counted on February 28 or March 1 depending on jurisdiction.
Age for legal and medical purposes
Legal age thresholds (18, 21, 65) are triggered on the exact birthday, not the day before or after. Medical age is often expressed in total months for young children (24 months rather than 2 years) because developmental milestones are more granular. The tool provides all formats so you can use the representation appropriate for your context.
| Age | Milestone | Notes |
|---|---|---|
| 13 | COPPA protection ends | Children under 13 have extra online privacy rights |
| 16 | Driving (most US states) | Learner permit; full licence typically at 17–18 |
| 18 | Age of majority | Legal adult: vote, sign contracts, join military |
| 21 | Alcohol (US) | Legal drinking age in the United States |
| 62 | Early Social Security | Earliest US Social Security benefit claim age |
| 65 | Medicare eligible | US federal health insurance eligibility |
Worked examples
Exact age between two dates
Inputs: 1 Jan 2000 → 1 Jan 2025
Result: 25 years, 0 months, 0 days · 9,132 days lived
Age with months and days
Inputs: 15 Jun 1990 → 20 Sep 2024
Result: 34 years, 3 months, 5 days
Glossary
- Gregorian calendar
- The internationally accepted civil calendar, with 365 days per year and a 366-day leap year every 4 years.
- Leap day
- February 29, which occurs only in leap years.
- Age of majority
- The legal age at which a person is considered an adult, typically 18 in most countries.
- Gestational age
- Age measured in weeks from the start of the last menstrual period, used for newborns and infants.
Related reading
Frequently Asked Questions
Why use Age Calculator?
- Calculates age in years, months, and days with full Gregorian calendar precision
- Reveals the exact day of the week you were born alongside total hours lived
- Counts down the precise number of days until your next birthday
- Accepts any past or future target date, not just today
Common use cases
- Verify exact age in years and months for a school enrolment or sports eligibility form
- Calculate how many days a grandparent has been alive for a milestone birthday card
- Determine a person's age on a specific historical date for genealogy research
- Confirm whether someone meets the legal age threshold before signing a contract
- Find out the day of the week you were born as a fun personal discovery
Get weekly tool tips & updates
New tools, power-user tips, and productivity hacks — delivered free every Friday.
No spam, ever. Unsubscribe with one click.
Related Calculators
Date Difference Calculator
Calculate the exact number of days, weeks, months, and years between two dates. Includes a working-days count — free, instant, and accurate.
Add / Subtract Days from Date
Add or subtract days, weeks, months, and years from any date. Find a future or past date instantly. Free online date arithmetic calculator.
Time Zone Converter
Convert time across global time zones with UTC offsets, daylight-saving awareness, and side-by-side city comparisons for accurate meeting planning.
Countdown Timer
Create countdown timers to any event. See days, hours, minutes, and seconds remaining. Save multiple countdowns and share them. Free online countdown timer.
BMI Calculator
Calculate your Body Mass Index (BMI) instantly. Supports metric (kg/cm) and imperial (lbs/ft+in) units. Free online BMI calculator.
Percentage Calculator
Calculate percentages instantly. Find what X% of a number is, what percentage X is of Y, or calculate percentage change.
Explore all Calculators.