Age in Weeks Calculator
See your age as a number of weeks. The result shows whole weeks plus the extra days, so it is easy to compare with a baby's age or the length of a project.
Choose your date of birth to see the result. Nothing is sent to a server; the calculation runs in your browser.
What this calculator measures
A week here is seven elapsed days, counted from the calendar date you were born. The headline number is the count of completed weeks, and the line under it adds the remaining days so nothing is rounded away. A person who has lived 1,000 days, for example, has completed 142 weeks and has 6 days left over.
This differs from the week numbers printed on calendars. ISO week numbers label weeks of a given year from 1 to 52 or 53 and say nothing about how long ago something happened. If you want to know which week of the year a date falls in, a calendar is the right tool; if you want elapsed time in weeks, this is.
| Age | Weeks | Months |
|---|---|---|
| 1 year | 52 | 12 |
| 5 years | 261 | 60 |
| 10 years | 522 | 120 |
| 18 years | 939 | 216 |
| 30 years | 1,565 | 360 |
| 50 years | 2,609 | 600 |
| 65 years | 3,392 | 780 |
| 80 years | 4,174 | 960 |
Where weeks are the natural unit
Parents often track a baby's age in weeks during the first months, before switching to months. Weeks are also the natural unit for course lengths, sprint cycles, training blocks and fixed-term notices.
A year contains about 52.18 weeks, not 52, because 365.2425 days divided by 7 leaves a remainder of 1.24 days. Over a long life that adds up: an 80-year-old has lived about 4,174 weeks, which is roughly 4,160 if you wrongly assume 52 weeks a year.
- Dividing days by 7 gives total weeks; the remainder is the extra days.
- Weeks since birth rises by exactly one every seven days, regardless of month lengths.
- Months are not a fixed number of weeks, so converting weeks to months is only approximate.
Weeks and months compared
The result grid also shows full calendar months. These are counted by date, so a person born on the 31st reaches a new month on the last day of shorter months instead of skipping it. Weeks and months answer different questions, and the two will not line up neatly: 52 weeks is 364 days, one day short of a calendar year.
Frequently asked questions
How many weeks are in a year?
52 weeks plus 1 or 2 extra days: 365 days is 52 weeks and 1 day, and a leap year of 366 days is 52 weeks and 2 days. On average a year is about 52.18 weeks.
How many weeks old is a baby at 12 months?
About 52 weeks. Exactly one year after birth the baby is 52 weeks and 1 day old, or 52 weeks and 2 days if a leap day was included.
Does the calculator count partial weeks?
The large number shows completed weeks only. The caption under it adds the leftover days, and the grid shows the exact total in days, hours and minutes.
Is this the same as the week number of the year?
No. Week numbers such as week 40 of 2026 label a calendar position. This tool measures how many seven-day periods have elapsed since a date.
How accurate is the result?
It is exact for calendar dates. The only assumption is that today's date comes from your device's clock and time zone.