How to Calculate Weeks Between Two Dates
Finding the number of weeks between two dates is a two-step process: first calculate the total number of days, then divide by 7.
The Formula
- Total days = End date − Start date (in days)
- Full weeks = floor(Total days ÷ 7)
- Remaining days = Total days mod 7
For example, 45 days between two dates = 6 weeks and 3 days.
Quick Reference
| Days | Weeks | Remainder |
|---|---|---|
| 7 | 1 | 0 days |
| 14 | 2 | 0 days |
| 30 | 4 | 2 days |
| 45 | 6 | 3 days |
| 60 | 8 | 4 days |
| 90 | 12 | 6 days |
| 180 | 25 | 5 days |
| 365 | 52 | 1 day |
Common Uses
- Pregnancy tracking: Pregnancies are measured in weeks (typically 40 weeks from last menstrual period).
- Project planning: Sprints and milestones are often planned in weekly intervals.
- School terms: Academic semesters run 15–16 weeks; quarters run 10–11 weeks.
- Notice periods: Employment contracts often specify notice in weeks (2 weeks, 4 weeks, etc.).
- Training programs: Fitness plans, courses, and certifications are structured around weekly cycles.
- Rental agreements: Short-term rentals may charge by the week.
Weeks in Common Time Periods
| Period | Weeks |
|---|---|
| 1 month (30 days) | 4 weeks 2 days |
| 1 quarter (91 days) | 13 weeks |
| 1 semester (120 days) | 17 weeks 1 day |
| 6 months (182 days) | 26 weeks |
| 1 year (365 days) | 52 weeks 1 day |
| 1 leap year (366 days) | 52 weeks 2 days |
Business Days vs Calendar Days
When counting weeks for work purposes, note that a calendar week has 7 days but only 5 are business days (Monday–Friday). Over 10 calendar weeks, you get 50 weekdays and 20 weekend days. The calculator breaks this down for you automatically.