Age Calculator
Calculate exact age in years, months, days, total days, and total weeks from any date of birth.
How to use this tool
- 1Enter a date of birth using the 'Date of birth' date picker.
- 2The 'As of date' defaults to today — change it to calculate age at a different date.
- 3The age breakdown (years, months, days) and totals (days, weeks) appear instantly.
About Age Calculator
Calculating an exact age requires more than subtracting years — you need to account for whether the birthday has occurred yet in the current year, and how many days remain in the current month. This calculator uses a three-step algorithm: subtract years, then adjust months (borrowing from years if negative), then adjust days (borrowing from months using the actual days in the previous month). The result shows years, months, and days as a breakdown, plus total days (millisecond difference divided by 86,400,000) and total weeks (total days divided by 7, floored). The 'As of date' defaults to today but can be set to any date — past or future — to calculate age at a specific point in time. The date of birth input is capped at the 'as of' date. HR professionals verifying employee ages, parents tracking milestones, and developers building age-gated features are the primary users.
Frequently asked questions
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