Age Calculator
Enter a date of birth to get an exact age plus total months, weeks and days.
Date & Time Calculators
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Age Difference Calculator
The gap between two birth dates, precisely.
Age Difference Calculator tool
Today by default.
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Age difference
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In days
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First person's age
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Second person's age
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Age ratio today
| Measure | Value |
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About the Age Difference Calculator
Age Difference Calculator works out the gap between two birth dates in years, months and days, and gives both ages as at a date you choose. The calendar arithmetic is exact: month lengths and leap years are handled by the browser's own calendar rather than approximated at 30 or 365.25 days.
The years-months-days form is the one people mean by an age gap, and it is not the same as dividing the day count by 365.25. A gap of 1,699 days is four years, seven months and twenty-three days, and which months those are affects the answer -- a gap spanning February differs from one spanning July.
The age ratio is included because it shows something the gap alone does not: a fixed gap shrinks in relative terms. Five years between a ten-year-old and a five-year-old is a ratio of two to one; the same five years at forty and thirty-five is barely one and a sixth.
The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.
Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.
Looking for something this does not cover? FreeToolStation.com is a second collection of the same kind of everyday tools, and it is worth a look if age difference calculator is only part of what you are working on.
How to use the Age Difference Calculator
- Enter first birth date, second birth date and ages as atDecimals are fine, and thousands separators are accepted and ignored.
- Read the age difference, in days and first person's ageThe figures update as you type. The Calculate button is there if you would rather press something, but nothing waits for it.
- Copy or check the resultCopy the summary with the copy button, or open the table to check it row by row.
Features
- Shows age difference, in days, first person's age, second person's age and age ratio today together, so you are not running it twice
- A results table you can read across
- Updates as you type, with no button to press and no page reload
- Copy the result in one click
- Free, no sign-up, and it runs entirely in your browser
Who uses this tool
The age difference calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:
- Finding the exact gap between two birthdays
- Working out two ages as at a particular date
- Checking an age gap for a form or application
- Comparing sibling ages precisely
Frequently asked questions
Why not just divide the days by 365?
Because years are not all the same length and months vary from 28 to 31 days. The exact years-months-days figure needs the real calendar, which is what this uses.
Can I use a date other than today?
Yes. The comparison date sets when the two ages are measured, which is useful for forms that ask for ages at a particular date.
Does it handle leap years?
Yes, including 29 February birthdays, which are handled by the calendar rather than by a special case.
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If the age difference calculator is not quite what you need, these other free tools solve closely related problems, and there are 13 more in date & time calculators.
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Checked and rebuilt on 2026-10-14. The method this calculator uses is described in the section above, and corrections go through the contact page.