Everything runs in your browser with no data upload. If you need a figure in months only - for example for a baby's growth chart or a pet's age - the Age In Months Calculator gives that directly, and the Days Between Dates Calculator handles any other date pair.
Calculator
How to use the Age Calculator
- Enter the date of birth in the first field.
- Optionally set an "as of" date to see the age on a past or future day.
- Read the exact age split into years, months and days.
- Check the totals in months, weeks and days plus the next birthday countdown.
About this tool
The Age Calculator is built for speed and accuracy: every calculation runs in your browser, so your data never leaves your device and the result updates as you type. It works equally well on a phone, a tablet or a desktop, and it is free to use as many times as you like.
Common use cases
- Filling in forms that need an exact age.
- Working out age on a future date such as school enrolment.
- Counting down to a milestone birthday.
- Checking a pet's or a child's age in months.
Tips for the best result
- Use the latest figures you have - even a small change in rate or term can shift the outcome by hundreds.
- For annual figures, divide by 12 to get a monthly number you can compare with the result.
- Bookmark this page and revisit the calculation as the inputs change.
Frequently asked questions
Does it account for leap years?
Yes. The calculation is based on real calendar dates, so leap days are included automatically.
Can I calculate an age in the future?
Yes. Set the "as of" date to any future day and the calculator returns the age you will be on that date.
Why do weeks differ from another site?
Some sites count complete weeks from a Monday. Here weeks are simply total days divided by seven and rounded down.
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