Weeks Between Dates Calculator
Count the weeks between two dates as a decimal and as full weeks plus days, with an option to include the end date, weekdays and weekend days in the span, ISO week numbers, calendar weeks touched and a week-by-week table.
How it works
Days = end date − start date (+ 1 if the end date is included) · weeks = days ÷ 7 · full weeks = ⌊days ÷ 7⌋, leftover days = days − 7 × full weeks · weekend days = 2 per full week + the Saturdays and Sundays among the leftover days
The calculator counts the calendar days from the start date up to the end date and divides by seven. The decimal answer suits planning and pregnancy-style counting; the full-weeks-plus-days answer is what you say out loud (“25 weeks and 6 days”). By default the start date is counted and the end date is not, the same way a week from Monday is the next Monday. Turn on “Include the end date” when both days are part of the period, such as a course, leave or rental that runs through the end date. Because every full week holds exactly five weekdays and two weekend days, the weekday count only needs to check the leftover days. The calculator also lists the ISO week number of each date (weeks start on Monday and week 1 contains January 4) and how many calendar weeks the span touches, which can be one more than the full weeks when the span starts mid-week. Dates are plain calendar dates, so daylight-saving changes never shift the count.
Worked example
From Thursday, January 1, 2026 to Wednesday, July 1, 2026 is 181 days. 181 ÷ 7 = 25.86 weeks, or 25 full weeks and 6 days. The 25 full weeks hold 50 weekend days, and the 6 leftover days (Thursday to Tuesday) add a Saturday and a Sunday, so the span has 52 weekend days and 129 weekdays. With the end date included it is 182 days — exactly 26 weeks.
Frequently asked questions
Does it include both end dates?
By default it counts the start date but not the end date, so Monday to the next Monday is 1 week. Turn on “Include the end date” to count both days; the total then grows by one day.
Can the end be before the start?
Yes. The dates are swapped automatically, the result is shown as a positive span, and a note says the swap happened.
How many weeks are in a year?
A common year has 365 days, which is 52 weeks and 1 day (52.14 weeks); a leap year has 52 weeks and 2 days. Some years have 53 ISO week numbers because of how the weeks line up with January 4.
What are “calendar weeks touched”?
The number of separate calendar weeks (Monday–Sunday, or Sunday–Saturday if you choose) that contain at least one day of the span. A 7-day span that starts on a Wednesday touches 2 calendar weeks even though it is exactly 1 week long.
What is an ISO week number?
In the ISO 8601 system, weeks start on Monday and week 1 is the week that contains January 4 (the first week with a Thursday). Dates at the very start or end of a year can belong to week 52 or 53 of the previous year, or week 1 of the next.
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This calculator is for educational purposes. Double-check important results before acting on them.