How to Calculate Your Exact Age
Working out an exact age in years, months and days is trickier than it looks — here's why leap years and month lengths matter, and how to get it right every time.
Your age in years is easy. Your exact age — years, months and days — is surprisingly fiddly, because months have different lengths and leap years add a day. This guide explains the pitfalls and how to get an accurate answer for any two dates.
Example
This is a sample result, not your calculation. Enter your own values to replace it.
Enter a date of birth and calculate the exact age.
Exact age
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In other units
- Total months
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- Total weeks
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- Total days
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- Total hours
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- Total minutes
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- Total seconds
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Check your dates
Enter a valid date of birth on or before the date to calculate the age at.
Why simple subtraction fails
You might think you can just subtract the birth date from today. But what is “one month” — 28 days? 30? 31? And how many February 29ths fell in between? Doing it by hand, it’s easy to be off by a day or two. The reliable method counts complete years first, then remaining whole months, then leftover days — borrowing correctly from the previous month when needed.
Leap years matter
Between 2000 and 2020 there were five leap days (2000, 2004, 2008, 2012, 2016), so that span is 7,305 days, not 20 × 365 = 7,300. Any accurate age or duration calculation has to count those extra days — which is exactly what the calculator above does.
When exact age is more than trivia
- Legal thresholds — driving, voting, retirement benefits often hinge on an exact date.
- Medical dosing and milestones — especially for infants, measured in weeks and months.
- Countdowns — days until a birthday or anniversary.
Age at any date
You aren’t limited to “today.” Set the second date to any point in the past or future to find how old someone was — or will be — on that day. Useful for planning events, checking eligibility, or settling a friendly argument.
Get your exact age, plus totals in months, weeks and days, from the age calculator. To measure the gap between any two dates, use the date calculator.