Projects are planned in weeks. So are pregnancies, training plans, school terms and notice periods. But calendars show days, and counting weeks across month boundaries by hand is where mistakes creep in.
The formula
Weeks between two dates = total days ÷ 7.
The whole number is the full weeks; the remainder is the extra days. For example, 1 March to 15 April is 45 days, which is 6 weeks and 3 days (6 × 7 = 42, plus 3).
The hard part is not the division — it is getting the total days right. Months have 28, 29, 30 or 31 days, and leap years add 29 February.
How to count weeks between two dates
- Open the free Date Difference Calculator.
- Pick the start date and the end date.
- Read the results: the difference in years, months and days, the total days, and the weeks and days.
Tick Include the end date in the count if both the first and the last day should count — for example, a holiday from Monday to Sunday is 7 days, not 6.
The off-by-one trap
"From 1 to 8 March" can mean 7 days (the gap between the dates) or 8 days (every calendar day you touch). Decide which you need before you count:
- Deadlines and ages use the gap: end minus start.
- Bookings, leave and events often count both ends — include the end date.
Common uses
- Project plans: how many sprint weeks fit before a launch date.
- Pregnancy: due dates are counted in weeks from the first day of the last period. Always confirm with your doctor or midwife.
- Notice periods and contracts: "four weeks' notice" from a given date.
- Countdowns: weeks left until a wedding, exam or holiday.
If you only need working weeks, use the Business Days Calculator, which skips weekends and any holidays you enter.
FAQ
How many weeks are in a year? 52 weeks and 1 day (52 weeks and 2 days in a leap year).
How many weeks are in a month? About 4.35 on average — between exactly 4 (February in a normal year) and 4 weeks and 3 days.
Does the calculator handle leap years? Yes. It works from real calendar dates, so 29 February is counted when it exists.
Try it now
Get the exact weeks and days with the free Date Difference Calculator.
Related reading
See How to Calculate Days Between Two Dates and How to Count Business Days Between Two Dates. Browse the full blog for more guides.