“How old is that, exactly?” is a surprisingly fiddly question once you go past whole years. Months have different lengths, leap years shift the math, and counting on your fingers from a birth date to today is easy to get wrong. The Age Calculator does it precisely: enter a date of birth and it returns the exact age in years, months, and days, plus totals in months, weeks, days, and hours. Leave the second field blank to measure to today, or set it to any date to find an age at a past or future moment. It’s handy for filling in forms, working out eligibility, planning milestones and anniversaries, or just settling the question of exactly how many days you’ve been around.
Age Calculator
Find an exact age in years, months, and days from a birth date.
How to use the Age Calculator
- Enter the date of birth in the first field.
- Optionally set a second date. Leave it blank to calculate age as of today, or pick any date to measure the age at that point.
- Press Calculate (or just change a date) to see the result update instantly.
- Read the breakdown. The top shows years, months, and days; below it you get total months, weeks, days, and hours.
Why use this age calculator
- It’s exact, not rounded. The calculation properly borrows days from the correct preceding month and accounts for leap years, so the years/months/days figure is accurate rather than approximate.
- Any two dates. It isn’t limited to “age today” — set a target date to find how old someone was (or will be) on a specific day, useful for eligibility cut-offs and anniversaries.
- Multiple units at a glance. Seeing the same span expressed in months, weeks, days, and hours is useful for planning, record-keeping, and the occasional fun fact.
- Private and instant. All math happens in your browser; no dates are uploaded or stored, and there’s no signup.
Example calculations
| Date of birth | Measured to | Result |
|---|---|---|
| 15 Jun 1990 | 7 Jul 2026 | 36 years, 0 months, 22 days |
| 29 Feb 2000 | 28 Feb 2025 | 24 years, 11 months, 30 days |
| 1 Jan 2010 | 1 Jan 2026 | 16 years, 0 months, 0 days |
How the math works
The calculator subtracts the birth date from the target date one unit at a time. It starts with days; if the target day is earlier in the month than the birth day, it borrows the number of days in the month immediately before the target month — which is what makes leap years and short months come out right. It then does the same for months and years. This is the same day-count logic used for everything from interest accrual to eligibility rules, and it’s why the result can differ from a naive “subtract the years” estimate. If you’re curious about the calendar rules underneath — particularly the leap-year cycle that keeps the seasons aligned — the overview of the Gregorian calendar is a clear explainer.
Frequently asked questions
Does the calculator account for leap years?
Can I calculate age on a future date?
Why are total months and years/months slightly different?
What happens if the second date is before the birth date?
Are my dates kept private?
Is the age calculator free?
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