How your age in weeks is worked out
The calculator counts the whole days between your birth and today, then divides by seven. The weeks are whole weeks since the weekday you were born, so if you arrived on a Thursday, each new week of your life starts on a Thursday. Leap days are included automatically because it uses real calendar dates.
Working it out by hand
Work out your age in days (your age in years × 365, plus one for each leap day you've lived through, plus the days since your last birthday), then divide by 7. The whole number is your weeks and the remainder is your extra days. A year is 52 weeks and 1 day, or 52 weeks and 2 days in a leap year.
Ages in weeks
How many weeks old you are on some common birthdays. Where there are two answers, it depends on how many leap days fell in between.
| Birthday | Weeks old |
|---|---|
| 1st | 52 weeks and 1 or 2 days |
| 5th | 260 weeks and 6 days, or 261 weeks |
| 10th | 521 weeks and 5 or 6 days |
| 18th | 939 weeks and 1 or 2 days |
| 21st | 1,095 weeks and 5 or 6 days |
| 30th | 1,565 weeks and 2 or 3 days |
| 40th | 2,087 weeks and 1 day |
| 50th | 2,608 weeks and 6 days, or 2,609 weeks |
| 60th | 3,130 weeks and 5 days |
| 70th | 3,652 weeks and 3 or 4 days |
| 80th | 4,174 weeks and 2 days |
Week milestones
Round numbers of weeks make good excuses for a celebration, because hardly anyone knows when theirs falls.
| Week | Age when it arrives |
|---|---|
| 500 | about 9 years and 7 months |
| 1,000 | about 19 years and 2 months |
| 2,000 | about 38 years and 4 months |
| 3,000 | about 57 years and 6 months |
| 4,000 | about 76 years and 8 months |
4,000 weeks is not far off an average lifespan, which is why some people like to picture their whole life as a grid of about 4,000 small boxes, one for each week.
Questions
Why do parents count babies' ages in weeks?
Babies change so quickly that months are too coarse, and development checks and feeding guides are often given in weeks. Most people switch to months at around three months old, and to years at around two.
Does the week I was born count as week one?
Not here. Like your age in years, the count starts at zero: you're 0 weeks old for your first seven days. If you'd rather count your first week as week one, the calculator shows that too.
How many days old am I?
The days old calculator gives your exact count, and shows when you'll reach 10,000 days.
Is my birth date stored anywhere?
Only in your own browser, so you don't have to type it again on other pages of this site. It's never sent to us or anyone else.