How weeks to years are calculated
A week is seven days and a calendar year averages 365.2425 days, so the conversion is one division or its reverse.
years = weeks × 7 ÷ 365.2425 (1 year = 52.1775 weeks)
- A week is exactly 7 days. A calendar year averages 365.2425 days — 365 days three years in four, 366 in a leap year.
- Multiply your weeks by 7 for days, then divide by 365.2425 to get years. To go back, multiply years by 365.2425 and divide by 7.
- One year works out at 52.1775 weeks, so "52 weeks a year" is really 364 days — a day short of a common year.
- Counting inside one known year? Switch the year length above to 365 or 366 days, since a leap day may or may not fall in your span.
Worked example — 100 weeks × 7 = 700 days. 700 ÷ 365.2425 = 1.92 years — that is 1 year and 47.8 weeks, or about 23 months.
Common amounts converted
| Weeks | Years | Months | Days |
|---|---|---|---|
| 1 weeks | 0.0192 years | 0.2 months | 7 days |
| 2 weeks | 0.0383 years | 0.5 months | 14 days |
| 4 weeks | 0.0767 years | 0.9 months | 28 days |
| 8 weeks | 0.1533 years | 1.8 months | 56 days |
| 13 weeks | 0.2491 years | 3 months | 91 days |
| 26 weeks | 0.4983 years | 6 months | 182 days |
| 52 weeks | 0.9966 years | 12 months | 364 days |
| 104 weeks | 1.99 years | 23.9 months | 728 days |
| 260 weeks | 4.98 years | 59.8 months | 1,820 days |
| 520 weeks | 9.97 years | 119.6 months | 3,640 days |
Swipe the table sideways to see the rest.
To go the other way, switch the converter above to Years → weeks.
Things to consider
- Pregnancy weeks count from the first day of the last period, so 40 weeks is about 9 months and 1 week, not 10 months.
- Years of service, probation and notice periods count completed weeks — read the "years and weeks" line rather than the rounded decimal.
- A payroll or academic year of 52 weeks is 364 days, so an extra week appears every five or six years — that is the 53-week year.
- For a person's or pet's age, count real dates instead — the Age Calculator includes the leap days your span actually contains.
Frequently asked questions
How many weeks are in a year?
52 weeks and 1 day in a common year, 52 weeks and 2 days in a leap year. Averaged over the calendar, a year is 52.1775 weeks.
Why isn't a year exactly 52 weeks?
52 weeks is 364 days, one day fewer than a common year. Those leftover days add up, which is why some ISO years run to 53 weeks.
How many years is 100 weeks?
100 weeks is 700 days — 1.92 average years, or 1 year and 47.8 weeks.
Is 52 weeks the same as 12 months?
No. 52 weeks is 364 days, while 12 average months is 365.24 days, so a year is about 1.2 days longer than 52 weeks.
How do I turn years back into weeks?
Multiply the years by 52.1775, or switch this converter to Years → weeks and type the years instead.
Results are estimates for general information only, not financial, medical or professional advice.