Age Calculator
Your exact age in years, months and days — and how long until your next birthday.
What is the Age Calculator?
The Age Calculator works out exactly how old you are — not just in years, but in months, weeks, days, hours and minutes. Enter your date of birth and it returns your chronological age the way institutions actually calculate it: full years completed, then remaining months, then remaining days. It also tells you which weekday you were born on and counts down to your next birthday. People use it for school and job applications, visa and pension forms, medical intake documents, and legal paperwork where "about 34" is not an acceptable answer.
Chronological age sounds trivial until you have to compute it across a leap year or a month boundary. February 29th birthdays, someone born on the 31st in a month that has 30 days, and the difference between "age last birthday" and "age nearest birthday" all trip up manual arithmetic. This calculator handles each of those cases explicitly, and shows the working so you can check it.
Why use a free age calculator?
Years, months and days — not a decimal
Forms almost never want "34.6 years". They want 34 years, 7 months, 12 days. That is what you get, in the order institutions expect it.
Leap years handled correctly
February 29th birthdays and any span crossing a leap day are calculated against the real calendar, not an assumed 365-day year.
Age on any date, not just today
Set a target date to find your age as of a deadline — useful for eligibility cut-offs on school enrolment, sports categories and visa applications.
Next birthday countdown
See exactly how many days remain until your next birthday, and which weekday it falls on.
Nothing is uploaded
Your date of birth is personal data. It is processed in your browser and never sent to us, so there is no record of it anywhere.
How do you use the Age Calculator?
- 1
Enter your date of birth
Type or pick your birth date. The calculator accepts any valid date and will tell you immediately if the date does not exist — such as 31 February.
- 2
Set the "age at" date if you need to
It defaults to today. Change it to calculate your age as of a specific deadline, such as the first day of a school year or an application cut-off.
- 3
Read your exact age
The headline result is years, months and days. Below it you get the same span expressed in total months, weeks, days, hours and minutes.
- 4
Check the birthday details
The calculator also shows the weekday you were born on and the countdown to your next birthday.
How is age calculator calculated?
Age = (Y₂ − Y₁) years, (M₂ − M₁) months, (D₂ − D₁) days — with borrowingWhere:
- Y₁, M₁, D₁
- Year, month and day of birth
- Y₂, M₂, D₂
- Year, month and day of the target date (today by default)
- Borrowing
- If D₂ < D₁, borrow the number of days in the month before the target month and subtract 1 from the month count. If M₂ < M₁ after that, borrow 12 months and subtract 1 from the year count.
The simple version
Count the whole years since you were born. Then count the whole months since your last birthday. Then count the leftover days. If a subtraction goes negative, borrow from the next unit up — exactly like long subtraction, except a "month" is worth however many days that specific month actually had.
What does it look like in practice?
A straightforward date
Input
Born 14 March 1990 · Age on 10 August 2026
Result
36 years, 4 months, 27 days
From 14 March 2026 (the last birthday) to 10 August 2026 is 4 full months plus 27 days.
Borrowing across a month boundary
Input
Born 30 January 1995 · Age on 28 February 2026
Result
31 years, 0 months, 29 days
The 30 January birthday has passed, but 28 February has not reached the 30th, so we borrow the 29 days of January 2026 (a leap year) rather than assuming 30 or 31.
A leap day birthday
Input
Born 29 February 2000 · Age on 1 March 2026
Result
26 years, 0 months, 1 day
2026 is a leap year, so 29 February exists and the birthday lands on it. In a non-leap year, this calculator treats 1 March as the birthday — the convention used by most legal systems.
How accurate is it?
Age is computed against the real Gregorian calendar, using the actual number of days in each month and each year. There is no 365-day or 30-day approximation anywhere in the calculation, so the years-months-days result matches what a registrar or immigration officer would arrive at by hand.
- Leap years follow the full Gregorian rule: divisible by 4, except centuries, unless divisible by 400. So 2000 was a leap year and 1900 was not.
- For 29 February birthdays in a non-leap year, the birthday is treated as 1 March. This is the most common legal convention, but a few jurisdictions use 28 February — check which applies to you if it matters legally.
- Hours and minutes assume midnight on both dates unless you specify a time, since a birth certificate date has no timezone attached.
- This is chronological age. Medical "bone age", gestational age and insurance "age nearest birthday" are different measures calculated differently.
What should you know before using it?
The different ways age gets expressed, and where each one is used:
| Measure | What it means and where it is used |
|---|---|
| Age last birthday | Full years completed. The default on almost every official form, passport and legal document. |
| Age nearest birthday | Rounded to the closest birthday. Used by some life insurers, where it can raise your quoted age by a year. |
| Age next birthday | Always rounds up. Used in a minority of insurance products and some annuity calculations. |
| Total days lived | Used for milestone celebrations (10,000 days) and for some paediatric dosing calculations. |
| Gestational age | Counted in weeks from the last menstrual period, not from birth. See the pregnancy calculator. |
| Decimal age | Years as a decimal, e.g. 34.62. Used in growth charts and statistical research, rarely on forms. |
Which tools relate to the age calculator?
The age calculator is one of 21 calculators on this site. These are the ones most often used alongside it — either because they handle the next step in the same job, or because they answer a question this tool raises.
Pregnancy Calculator
Works backwards rather than forwards — from a last menstrual period to a due date and gestational age in weeks.
BMI Calculator
BMI interpretation depends on age: the adult categories do not apply to children and teenagers, who are read against age-and-sex percentiles instead.
Heart Rate Calculator
Maximum heart rate is derived directly from your age, so an accurate age changes every training zone it produces.
Sleep Calculator
Recommended sleep duration is banded by age group, from newborns through to older adults.
When should you use a age calculator?
Because the age calculator runs entirely in your browser, it suits work you would not want to hand to a third-party server — client files, unpublished drafts, anything under an NDA. These are the situations people reach for it in most often.
Official forms and applications
Visa applications, pension claims, school enrolment and job applications all ask for exact age or age as of a specific date. Getting it wrong can invalidate a submission.
Eligibility cut-offs
School year placement, youth sports categories, driving licence bands and retirement thresholds all depend on your age on one particular date — not today.
Medical and fitness baselines
Dosing, screening schedules and target heart-rate zones are age-derived, so clinicians and trainers need the precise figure.
Open the Medical and fitness baselinesMilestones and planning
Find the date you turn 10,000 days old, or how many days remain until a birthday you are planning around.
Frequently asked questions
How do you calculate age in years, months and days?
What is my age if I was born on 29 February?
Can I calculate my age on a future or past date?
Why does my age in months not match years × 12?
Is chronological age the same as biological age?
Is my date of birth stored anywhere?
Which weekday was I born on?
Is the age calculator safe to use?
This tool runs entirely inside your browser. Your text, files and settings are processed on your own device and are never uploaded to our servers — there is nothing for us to store, log or leak. You can confirm it yourself: open your browser DevTools, switch to the Network tab, and use the tool. You will not see an upload request. It also means the tool keeps working if your connection drops mid-task.
Where do these figures come from?
Every method, threshold and standard this page relies on, with a link to the document that defines it. Check them — a tool that will not show its sources is asking you to take its word for it.
- 1Introduction to Calendars
US Naval Observatory
Supports: The Gregorian leap-year rule (divisible by 4, except century years, unless divisible by 400) used in the age calculation.
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