Estimate, not a legal decision
Use the result as decision support and planning help. For high-stakes choices, confirm the details with the relevant authority, lender, employer, or adviser.
Tools
Age Calculator – Exact Age by Date
Calculate age on any date in completed years, months, weeks, and days, plus the countdown to the next birthday.
Your age
Completed calendar periods and the countdown to the next birthday.
- Age in completed years
- 0
- Age in completed months
- 0
- Age in completed weeks
- 0
- Age in days
- 0
- Days until next birthday
- 0
Number of birthdays already reached.
Details
Total completed calendar months.
Total completed seven-day periods.
Exact number of full days between the dates.
0 means the birthday falls on the selected date.
Analysis & guidance
Convert shorter periods
Use the time converter for days, hours, and minutes.
Health calculations
The BMI calculator uses age as context but cannot replace medical advice.
Compare differences
Use the percentage calculator to compare ages or time spans relatively.
Common age questions
How is exact age calculated?
Enter both dates. The calculator counts completed years and reports total completed months, weeks, and days.
Why is age in months not always years times twelve?
Only completed calendar months count. The current month is excluded until its matching day is reached.
How are leap years handled?
Actual calendar days include leap days automatically. A 29 February birthday is mapped to 28 February in other years.
Can I calculate age on a past date?
Yes. Change the comparison date to see how old someone was or will be on a particular day.
Completed years follow the calendar
A year is completed only when the birthday has been reached in that calendar year. Subtracting year numbers alone can be one year too high.
Months, weeks, and days answer different questions
Months follow calendar boundaries, while weeks and days use the exact number of full days between the selected dates.
Birthdays on 29 February
In years without 29 February, the calculator treats 28 February as the birthday for a consistent countdown. Specific legal rules may differ.
How to use the age calculator
Enter the date of birth, then choose the date on which you want to know the age. Today is selected by default, but a past or future comparison date works just as well. This makes the tool useful for both “how old am I?” and age-at-event questions.
Completed years are more than year subtraction
Someone born on 20 October 1990 has not turned 36 on 1 January 2026, even though 2026 minus 1990 equals 36. The birthday must be reached first. The calculator therefore checks the month and day before counting a completed year.
Age in months follows completed calendar months. Weeks and days instead use the exact number of full days between the dates. These totals are alternative views of the same period and should not be added together.
Leap years and 29 February
Leap days are automatically included in the total number of days. For a person born on 29 February, this calculator uses 28 February as the birthday in a non-leap year. That is the tool's consistent calculation rule; a legal or contractual age threshold may apply a different convention.
When to verify the answer
This is a practical date tool, not a legal determination. Check the responsible authority's rules when an exact age threshold affects eligibility, pensions, insurance, or a contract. Dates are calculated without times of day, so every difference represents complete calendar days.
How to read this calculator
These results are meant as guidance. They are based on rules, assumptions, and simplified models that can differ from your exact real-world situation.
Methodology
Each calculator uses defined inputs, assumptions, and logic. We explain the broader approach on the methodology page.
Read methodologySources and updates
Important calculators should be traceable back to official rules, public guidance, or other clearly stated references.
Read about sourcesCommon age questions
Time Converter – seconds, minutes, hours and days
Use the time converter for days, hours, and minutes.
Turn raw seconds into a clear duration
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The BMI calculator uses age as context but cannot replace medical advice.
One BMI calculator for adults, children, and youth with WHO-aligned guidance.
Open BMI calculatorPercentage Calculator
Use the percentage calculator to compare ages or time spans relatively.
Four common percentage questions in one calculator
Run calculationDate Difference Calculator – Count Days
Use Date Difference Calculator – Count Days to compare the next part of the same scenario.
Calendar days and weekdays in one clear result
Count days