How to calculate an age
- Enter the date of birth.
- Leave the second date blank to use today.
- Pick a second date to find the age on that day.
- Press Calculate age.
- Copy the results for your form.
What this age calculator gives you
- Exact age in years, months and days.
- Totals in months and weeks plus days and hours.
- The weekday of the birth date.
- A countdown to the next birthday with its weekday.
- An age on any past or future date.
- Private math in your browser with no upload.
Why exact age is harder than it looks
A simple year subtraction gives the wrong answer much of the time. Take someone born in December 1990. In January 2026 they are not 35 yet. They turn 35 only after their December birthday.
The right answer compares the month and day as well. It also handles a birthday that has not arrived yet this year. An age calculator does this for you without mistakes.
Month math is trickier still. Months have different lengths. So "one month after 31 January" has no obvious answer. This tool borrows days from the month before when the day count goes negative. That rule matches how people actually count.
When you need an exact age
| Situation | Why the exact age matters |
|---|---|
| Medical forms for young children | Doctors track age in months |
| School enrollment | Cutoffs fall on an exact date |
| Insurance and pensions | Rates change on a birthday |
| Youth sports | Age groups use a set day |
| Visa and passport forms | Some ask for age on the date you apply |
The 29 February question
A leap day birthday shows up about once every four years. Most places treat the age as going up on 1 March in other years. A few use 28 February instead. This tool follows the more common 1 March rule.
This matters for hard age limits. Think of a driver's license, legal adulthood or an insurance band. Does it apply to you? Check which rule the agency or company uses.
How to read the totals
Most forms that ask for age in days want the total days figure. It counts real days including every leap day.
The hours figure comes from the day total. It treats every day as 24 hours. That is slightly off across daylight saving changes. At this scale the gap does not matter.
Total months counts complete months only. A child aged 3 years and 11 months shows 47 months and not 48. Medical and growth forms expect exactly that.
Age on a past or future date
Fill in the second date to see an age on any day. Want to know how old you will be at your wedding? Need someone's age on the day of an event? Need an age on a deadline for a form? The tool answers each one the same way.
A quick age calculator example
Enter a birth date of 15 March 2000. Leave the second box blank. The tool counts from that day to today. It shows the years, months and days in three boxes. Below them you see the total weeks and days. The last line shows how many days remain until the next 15 March and which weekday it lands on.
Common age calculator questions
Why does another site show a different month count?
Sites handle short months in different ways. This tool borrows days from the previous month. That matches how most people count.
Can I find the age of a pet or a building?
Yes. Enter any start date. The tool counts time the same way for anything.
Tips for forms and records
- Use the date format the form asks for.
- Give age in completed years unless the form says otherwise.
- Use total months for babies and toddlers.
- Check leap day rules for legal age limits.
Who uses an age calculator?
Parents fill out school and doctor forms. HR teams check retirement dates. Coaches confirm age groups. Genealogy fans work out ages from old records. Party planners count down to big birthdays.
Your date of birth stays private
A date of birth is personal data. Identity thieves value it. So it should never go to an unknown server. This tool does every step in your browser and sends nothing. Need days between any two dates? Use the date calculator. Want to add hours and minutes? Try the time calculator. Do you work with Unix time? The timestamp converter helps.