Divide by 7, and mind the remainder
A week is always exactly 7 days, so this conversion is exact — unlike months. Divide the days by 7 for the decimal answer; the whole part is full weeks and the remainder is the extra days. 30 days is 4 weeks and 2 days because 30 = 4 × 7 + 2.
Common values
| Days | Weeks (decimal) | Weeks and days |
|---|---|---|
| 7 days | 1.00 | 1 week |
| 14 days | 2.00 | 2 weeks |
| 30 days | 4.29 | 4 weeks, 2 days |
| 90 days | 12.86 | 12 weeks, 6 days |
| 280 days | 40.00 | 40 weeks (a pregnancy) |
| 365 days | 52.14 | 52 weeks, 1 day |
To turn a decimal back into days, multiply the fractional part by 7: 4.29 weeks → 0.29 × 7 ≈ 2 days.
Two things people get wrong
- A year is not a round 52 weeks. 365 ÷ 7 is 52 weeks plus 1 day, and a leap year adds a second spare day. That leftover is why the same calendar date shifts by a weekday each year.
- "Two weeks' notice" means 14 calendar days. That is usually about 10 working days once weekends are removed, which can trip up planning.
Common questions
How do I convert days to weeks?
Divide the number of days by 7. Any remainder is the leftover days. For example, 30 days is 4 weeks and 2 days, or 4.29 weeks as a decimal.
How many weeks are in a year?
52 weeks and 1 day, since 365 divided by 7 leaves a remainder of 1. A leap year has 52 weeks and 2 days. Under the ISO calendar a year has 52 or 53 numbered weeks.
Is 4 weeks the same as a month?
No. Four weeks is exactly 28 days, but a month is 28 to 31 days. The average month is about 4.35 weeks, so a month is usually a little longer than four weeks.
