The Age Calculator is a free tool that helps you calculate age using the formula Difference between the two dates expressed in years, months and days. Enter your values above and press Calculate to get years, months, days instantly, with a full step-by-step breakdown.
What is the Age Calculator?
The age calculator is a free online tool that helps you calculate age quickly and accurately. It applies the standard formula Difference between the two dates expressed in years, months and days to the values you enter and, when you press Calculate, displays the result together with a clear, step-by-step explanation of how the answer was reached.
Also known as: date of birth calculator, birth date calculator, dob calculator, age calculator by date of birth, birth calculator, age calculator online.
How to use the Age Calculator
- Enter your date of birth.
- Optionally set the 'as of' date.
- See your exact age.
Formula used
The age calculator is based on this formula:
Difference between the two dates expressed in years, months and daysEach term in the formula corresponds to one of the inputs explained below. The calculator performs the arithmetic for you and shows every step so you can check the working by hand if you wish.
Worked example
Suppose you enter DOB 1 Jan 2000. The calculator works as follows:
| Inputs | DOB 1 Jan 2000 |
|---|---|
| Working | diff to today |
| Result | e.g. 26 years |
Step-by-step calculation
- Apply the formula:
Difference between the two dates expressed in years, months and days - Substitute your values: diff to today
- Read the result: e.g. 26 years
Inputs explained
- Date of birth — the date of birth used in the calculation.
- Age at date (defaults today) — the age at date (defaults today) used in the calculation.
Understanding your result
- Years — the calculated years.
- Months — the calculated months.
- Days — the calculated days.
- Total days — the calculated total days.
Benefits and practical uses
The age calculator saves time and removes the risk of manual errors when you need to calculate age. It is useful for students, professionals and anyone who wants a fast, dependable answer. Results update the moment you press Calculate, work on any device, and can be copied or shared in a single click — and because the maths runs in your browser, your figures stay completely private.
Tips for an accurate result
- Keep all related inputs in the same units.
- Use the worked example above to confirm you are entering values in the right places.
- Review the assumptions below so the result fits your situation.
- Press Reset to clear everything and try a different scenario.
Common mistakes to avoid
- Entering values in the wrong unit (mismatched units give wrong answers).
- Leaving a required field empty — the calculator will ask you to fill it in.
- Rounding inputs too early, which can slightly change the result.
Assumptions and limitations
- Gregorian calendar.
Frequently asked questions
How is age calculated?
By counting complete years, then months, then days between the two dates.
How do I use the Age Calculator?
Enter your values in the fields, then press the Calculate button to see the result. Use Reset to clear the form and start again. Nothing is calculated until you click Calculate.
What formula does the Age Calculator use?
It uses the standard formula: Difference between the two dates expressed in years, months and days. The full step-by-step working is shown with every result so you can verify it.
What information do I need to use the age calculator?
You need: date of birth, age at date (defaults today). Sensible example values are pre-filled so you can see how it works.
Is the Age Calculator free to use?
Yes. Every DigiToolkit calculator is completely free, with no sign-up, no login and no usage limits.
Does the Age Calculator work on mobile phones?
Yes. The calculator is mobile-first and works on phones, tablets and computers in any modern browser.
Do I need to install an app?
No. The age calculator runs directly in your web browser — there is nothing to download or install.
Is my data private when I use this calculator?
Yes. All calculations run inside your browser. The numbers you enter are never uploaded to a server or shared with anyone.
How accurate is the Age Calculator?
It uses the generally accepted formula for age and computes to several decimal places. Results are accurate for the assumptions listed on this page.
Can I copy or share my result?
Yes. After calculating, use the Copy button to copy the result, or Share to copy the page link.
Why is nothing showing until I press Calculate?
By design, the calculator only computes when you press Calculate, so you can finish entering all your values first. Press Reset any time to clear everything.