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Age Calculator Calculate the exact age difference between two people in years, months, days, weeks, and hours.

Age Difference Calculator illustration
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Age Difference Calculator

Calculate the exact age difference between two people in years, months, days, weeks, and hours.

1

Enter Date of Birth

Select your date of birth using the date picker.

2

Set Target Date

Defaults to today — change to calculate age at any date.

3

View Age Details

See exact age in years, months, days, weeks, hours, and more.

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What Is Age Difference Calculator?

The Age Calculator computes your exact age between any two dates with precision down to the day. It shows your age in multiple formats: years/months/days, total months, total weeks, total days, and total hours. It also tells you what day of the week you were born and how many days remain until your next birthday. You can also calculate the age difference between any two dates by adjusting the target date — useful for finding the duration between historical events, employment periods, or any date-based calculations.

Why Use Age Difference Calculator?

  • Precise age calculation in multiple formats (years, months, days, weeks, hours)
  • Shows day of the week for any birth date
  • Countdown to next birthday
  • Flexible target date for historical or future calculations

Common Use Cases

Personal

Find your exact age in days, weeks, and hours for fun or milestone tracking.

Legal/Administrative

Calculate exact age for legal documents, eligibility requirements.

HR/Employment

Determine tenure or service duration between dates.

Historical

Find the exact duration between historical dates or events.

Technical Guide

The age calculation handles calendar month variations correctly: first subtracting years, then months, then days, with proper carry-over for months with different day counts. Total days uses the exact millisecond difference divided by 86,400,000 (ms per day). The next birthday calculation finds the birthday in the current year, and if it has already passed, moves to the next year. Day-of-week computation uses JavaScript's Date object which implements the proleptic Gregorian calendar.

Tips & Best Practices

  • 1
    Your age in days reaches 10,000 around age 27 — a milestone worth celebrating!
  • 2
    Leap year babies (Feb 29) can enter their birthday and see correct age calculations
  • 3
    Change the target date to calculate age at any point in time
  • 4
    Total hours is approximately your age in days × 24

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Frequently Asked Questions

Q How is age calculated exactly?
Age is calculated by finding the difference in years, then adjusting for months and days. If the current day is before the birth day in the month, one month is subtracted and the remaining days from the previous month are added.
Q When do I turn 10,000 days old?
You turn 10,000 days old approximately 27 years and 4.5 months after your birth date.
Q How are leap years handled?
The calculator correctly handles leap years. If you were born on February 29, your age is calculated accurately even in non-leap years.
Q Can I calculate age between any two dates?
Yes, change the target date to any date in the past or future. This is useful for calculating durations like employment tenure or time between events.
Q Is the total hours calculation exact?
Total hours is calculated as total days × 24. It does not account for the exact time of birth since only dates are used.

About This Tool

Age Difference Calculator is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.