Convert Days (d) to Weeks (wk)
1 day equals 0.142857 weeks.
Day to Week Converter
What Is a Day?
The day (d) is a unit of time equal to exactly 86,400 seconds or 24 hours. The civil day is the standard unit for calendrical purposes. It is accepted for use with the SI system, with the symbol d (ISO 80000-3).
What Is a Week?
The week is a unit of time equal to exactly 7 days (604,800 seconds). The seven-day week has ancient origins in Mesopotamia and became universal through religious traditions. It is standardized in ISO 8601, which defines Monday as the first day of the week for international use.
Days to Weeks Formula
The conversion is exact by definition:
weeks = days ÷ 7 exact
Since 1 week = 7 days exactly, dividing by 7 gives the precise result.
Worked Example
Convert 280 days (standard pregnancy duration) to weeks:
- Divide: 280 ÷ 7 = 40 weeks
A full-term pregnancy is 40 weeks from the last menstrual period — the most well-known days-to-weeks conversion.
Common Days to Weeks Conversions
| Days | Weeks | Context |
|---|---|---|
| 1 d | 0.143 wk | 1/7 of a week |
| 3 d | 0.429 wk | Common shipping estimate |
| 5 d | 0.714 wk | Standard work week (Mon-Fri) |
| 7 d | 1 wk | Exact — by definition |
| 10 d | 1.429 wk | Quarantine period (some diseases) |
| 14 d | 2 wk | Standard quarantine / biweekly pay period |
| 21 d | 3 wk | Common vacation length / "habit" period |
| 28 d | 4 wk | Shortest month (Feb) / menstrual cycle |
| 30 d | 4.286 wk | Average month length |
| 60 d | 8.571 wk | "Net 60" payment terms |
| 90 d | 12.857 wk | Quarter (business) / probation period |
| 365 d | 52.143 wk | Common year (52 weeks + 1 day) |
When You Need This Conversion
- Pregnancy tracking: Pregnancy is measured in weeks (40 weeks = 280 days). Trimesters: 1st = weeks 1-12 (84 days), 2nd = weeks 13-26, 3rd = weeks 27-40.
- Project planning: Sprint cycles in Agile development are 1-2 weeks. A 90-day project = ~13 weeks = 6-7 two-week sprints.
- Fitness programs: Training plans are structured in weeks. A "Couch to 5K" program is typically 9 weeks (63 days).
Frequently Asked Questions
How many weeks are in a year?
52.1429 weeks in a common year (365 ÷ 7). A leap year has 52.2857 weeks. ISO 8601 assigns either 52 or 53 numbered weeks per year.
How many weeks is 9 months (a pregnancy)?
A full-term pregnancy is 40 weeks (280 days) from the last menstrual period. This is approximately 9 months and 1 week in calendar terms.
How many days are in a work week?
The standard work week is 5 days (Monday-Friday) in most countries. Some countries use a 6-day work week; the 4-day work week is gaining traction in parts of Europe.
How do I convert weeks back to days?
Multiply by 7. Example: 12 weeks × 7 = 84 days. For weeks and days: 12.5 weeks = 12 weeks + 3.5 days = 87.5 days.
Days to weeks Conversion Table
Reference table with common days to weeks conversions. All values calculated with high precision.
Days to Weeks Table
10 to 1000000
Looking for the reverse? Convert Week to Day
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