Days to weeks
Multiply days by 0.142857 to get weeks.
30 d = 4.2857 wk
How to convert days to weeks
The week is exactly 7 days. The day is exactly 24 hours (86 400 seconds).
Worked example — 30 d: 30 × 0.142857 = 4.2857 wk.
Days to weeks table
| Days | Weeks |
|---|---|
| 1 d | 0.142857 wk |
| 7 d | 1 wk |
| 14 d | 2 wk |
| 21 d | 3 wk |
| 30 d | 4.2857 wk |
| 60 d | 8.5714 wk |
| 90 d | 12.8571 wk |
| 180 d | 25.7143 wk |
| 365 d | 52.1429 wk |
Reverse and related
About days and weeks
Day (d)
1 d = 0.142857 wkDefinition. Exactly 24 hours (86 400 seconds)
History and origin
The day is based on one rotation of the Earth and is fixed for timekeeping at exactly 24 hours, or 86 400 seconds. The natural day varies slightly, so a mean value is used.
Current use
Days are the basic unit of the calendar and of everyday durations.
Source: BIPM SI Brochure (2019); the second is defined by the caesium-133 transition
Week (wk)
1 wk = 7 dDefinition. Exactly 7 days
History and origin
The week is a seven-day cycle with ancient roots in Babylonian and Jewish tradition, tied to the seven classical planets and to religious observance. Unlike other time units it has no astronomical basis.
Current use
Weeks organise schedules and are used to count the length of pregnancies and projects.
Source: BIPM SI Brochure (2019); the second is defined by the caesium-133 transition
Where people use this
Days: calendars, durations. Weeks: schedules, pregnancy and projects. 7 days is exactly 1 week.
Every value is carried to full double precision; the display is rounded.
Both units are defined in BIPM SI Brochure (2019); the second is defined by the caesium-133 transition.
Questions people ask
How many days in a week?
One week is exactly 7 days.
How many weeks is 30 days?
30 days is about 4.3 weeks.
How many weeks is 90 days?
90 days is about 12.9 weeks.