Age in Weeks Calculator
See how many weeks old you are from your date of birth: complete weeks plus days, exact decimal weeks, and the dates of your 1,000-week milestones.
This calculator counts how many weeks old someone is from their date of birth. It gives the number of complete weeks with the days left over, the exact age as a decimal, and the dates when big round numbers such as 1,000 or 2,000 weeks are reached. Weeks are a handy unit for babies and toddlers, for “life in weeks” journaling, and for planning a 1,000-week or 2,000-week celebration.
How to use this tool
- Enter the date of birth.
- Leave the end date as today, or choose another date to see the age in weeks on that day.
- Read the complete weeks, the leftover days and the exact decimal figure.
- Check the milestone table for the dates of upcoming round-number weeks.
Formula
Total days = end date − date of birth
Weeks = ⌊total days ÷ 7⌋, leftover days = total days mod 7
The day count is the plain number of calendar days between the two dates, so leap days are included automatically. A new week of age always begins on the weekday of birth: someone born on a Saturday completes each week on a Saturday.
Example
For someone born on 1 January 2000, on 1 January 2026 the gap is 26 × 365 + 7 leap days = 9,497 days. Dividing by 7 gives 1,356 weeks and 5 days (about 1,356.71 weeks). Their 1,000th week was completed on 2 March 2019, and 2,000 weeks falls in May 2038.
Frequently asked questions
How many weeks old is a 1-year-old?
A year of 365 days is 52 weeks and 1 day, so on a first birthday a child is 52 weeks old (53 weeks would be reached a few days later). If the year includes 29 February, it is 52 weeks and 2 days.
When do you turn 1,000 weeks old?
1,000 weeks is 7,000 days, which is about 19 years and 2 months. The exact date depends on how many leap days fall in between, so use the milestone table.
Does it count the birth day itself?
No. The count starts at zero on the day of birth, the same way age in years works, so a baby is 1 week old exactly seven days after birth.
Why does the decimal figure differ from weeks plus days?
They are the same amount written two ways: 1,356 weeks and 5 days equals 1,356 + 5/7 ≈ 1,356.71 weeks.
Last updated: 2026-10-30