Age Calculator
Your exact age in years, months, days and weeks from a date of birth.
An age is rarely one number. Forms ask for completed years, a passport application wants it precisely, and people are curious about the days and the weeks. Counting across leap years by hand is where the arithmetic goes wrong.
Enter a date of birth and the date to measure at, and this calculator gives the completed age and the same interval expressed in months, weeks and days.
At a glance
- What you enter
- Date of birth, Measure age at
- What you get
- Completed years, Months since the last birthday, Days since the last month anniversary, Total months, Total weeks, Total days
- Formula shown
- Yes - every step, right below your results.
- Cost and privacy
- Free, no account needed, and nothing you type is stored.
See worked examples ↓ Read the FAQ ↓ Share this calculator ↓
How is this calculated?
Completed years, months and days come from the calendar difference between the two dates, the way a form would count them: for example 34 years, 7 months and 12 days. The same interval is then expressed as total months, total weeks and total days, which are the figures people quote when they say an age in months or days.
Feb 29 is handled as a real date, and a birth date that falls on a day a shorter month does not have is clamped to the end of that month. A person born on 29 February turns a year older on 1 March in most legal systems, which is why the calendar age here can differ by a day from an official record.
Days to the next birthday: 58
Hours since birth: 16,128
What does this mean?
The age is under thirteen, which is the range where age is usually quoted in months for health and development purposes.
Measured at {measure_date_label}, the age is {years.with_unit}, {months.with_unit} and {days.with_unit}. That is {total_months.with_unit} in total, or {total_weeks.with_unit} and {total_days.with_unit}, which is 16,128 hours since birth. The next birthday is {next_birthday_label}, in {days_to_next_birthday.with_unit}.
What should I do next?
-
Use completed years for official forms
Almost every form asks for completed years, which is the first figure above. The months and days are for curiosity or for medical records.
-
Check the rule where the birth date is 29 February
Most legal systems treat 1 March as the birthday in non-leap years, which can make an official age differ by a day from a calendar calculation.
-
Count the days for a milestone
For a tenth birthday, a twenty-first or a significant anniversary, the total days figure is the one that makes the milestone feel real.
Open the Countdown Calculator →
Results are estimates for general information only - always verify with a professional or official source before acting on them.
How to use the Age Calculator
- 1 Enter Date of birth
- 2 Enter Measure age at - Today by default, or a future date.
- 3 Press Calculate. You get Completed years, Months since the last birthday, Days since the last month anniversary, Total months, Total weeks, Total days, and every intermediate step stays visible under “How is this calculated?”
- 4 Change one number at a time to see what moves the result - that is usually the most useful thing a calculator can tell you.
Worked examples
Real numbers run through this calculator. Open any example to load it into the form above and change it.
Someone born in June 1990, measured in January 2026
A working age in completed years, months and days.
You enter
- Date of birth
- 1990-06-15
- Measure age at
- 2026-01-20
You get
- Completed years
- 35
- Months since the last birthday
- 7
- Days since the last month anniversary
- 5
- Total months
- 427
- Total weeks
- 1,857
- Total days
- 13,003
The age is 35 years, 7 months and 5 days, which is 427 months or about 12,998 days. The next birthday is on 15 June 2026, which is 146 days away.
A child born on 29 February 2024, measured at the start of 2026
A leap day birth date, where the birthday has to be clamped in a non-leap year.
You enter
- Date of birth
- 2024-02-29
- Measure age at
- 2026-01-01
You get
- Completed years
- 1
- Months since the last birthday
- 10
- Days since the last month anniversary
- 3
- Total months
- 22
- Total weeks
- 96
- Total days
- 672
The age is 1 year, 10 months and 3 days, or 22 months in total. The next birthday falls on 28 February 2026 under the clamping rule, which is 58 days away.
Guides that go with it
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Frequently asked questions
How is the age counted?
The completed age is the calendar difference: 34 years, 7 months and 12 days means 34 whole years have passed, then 7 whole months and then 12 days. That is not the same as dividing the total days by 365.25, which is why a calculator is more reliable than an estimate.
The total months, weeks and days are the same interval expressed three other ways. Forms ask for completed years, so that is the figure to use.
What happens with a 29 February birth date?
The date is handled as a real date, and the birthday in a non-leap year is clamped to the end of February. Most legal systems treat 1 March as the birthday in those years, so an official record can differ from the calendar age by a day.
For anything where the exact day matters, such as an eligibility date, use the official rule of the country or body asking rather than this page.
Can I measure the age at a future date?
Yes. The measure date is a field of its own, so setting it forward gives the age someone will be on a future date, which is what a countdown to a milestone needs.
The countdown calculator is the more useful page once the question is "how long until", because it also counts working days and weekends in between.
Does the calculator know my time zone or the current time of day?
No. It works in whole days, so the age changes at the start of the birthday rather than at the hour someone was born. That matches how ages are normally counted and how forms are filled in.
For a legal or medical purpose where the hour matters, the time of birth is part of the record and is outside what a date calculator can tell you.