Age Calculator
Calculate exact age in years, months, and days between two dates.
Inputs
Leave blank to use today.
Age
26 years, 7 months, 9 days
Total Months
319
Total Weeks
1,388
Total Days
9,718
Step by step
Reference dates
January 1, 2000 → August 10, 2026
Subtract year, month, and day components
years: 2026 − 2000 = 26
Day and month components are adjusted with borrowing when the end day or month is smaller than the birth day or month.
Exact age (calendar-aware)
= 26 years, 7 months, 9 days
Total elapsed days (millisecond difference ÷ 86 400 000)
9,718 days
= 1,388 weeks
How it works
Age is computed by subtracting the year, month, and day components separately and borrowing when needed — the same way you'd work it out on paper. This correctly accounts for different month lengths and leap years.
Formula
Age = calendar difference between date of birth and reference date, computed by subtracting year/month/day components and borrowing from the next-larger component when the end value is smaller than the birth value.
- borrowing
- When end-day < birth-day, one month is subtracted and the days of the preceding month are added to the day difference
- totalDays
- Math.floor((end − birth) in milliseconds ÷ 86 400 000)
- totalWeeks
- Math.floor(totalDays ÷ 7)
Frequently Asked Questions
Why not just divide days by 365.25?
That gives an approximation. Proper age uses calendar components so that, for example, someone born on Feb 29 or at month boundaries gets an exact, correct age.
Can I find my age on a future date?
Yes — enter any date in the 'Age at Date' field to see how old you'll be (or were) on that day.