Count Weeks Between Dates or Project Any Deadline
Enter two dates to count the weeks between them, or enter a date plus a week count to find when a deadline falls. Supports calendar weeks and business weeks (Mon-Fri).
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Week Calculator
Count weeks between two dates, find a future deadline, or work back from a due date. Supports calendar and business weeks.
Options
Inputs
Weeks Between Any Two Dates
Pick a start date and an end date, then click "Calculate Weeks Between Dates" to see the exact number of weeks and remaining days. Toggle business weeks mode to count only Monday-through-Friday working days.
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Find a Future Deadline
Know the start date and how many weeks you have? Enter both and click "Add Weeks to Start Date" to get the exact end date. Useful for project planning, countdowns, or figuring out when a delivery window closes.
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Work Back from a Deadline
Have a fixed end date and need to know when to start? Enter the end date, enter the number of weeks needed, and click "Subtract Weeks from End Date" to get the start date. Works in both calendar and business week modes.
Try It NowThree ways to calculate in three steps
Choose your calculation mode
Decide what you want: count weeks between two dates, add weeks to a start date, or subtract weeks from an end date. Fill in the two values the mode needs.
Set options
Pick a display format for dates (YYYY-MM-DD, MM/DD/YYYY, or DD/MM/YYYY) and toggle business weeks mode if you want to exclude weekends.
Click the matching button
Press the button for your mode. The result appears immediately below, showing the week count with leftover days or the calculated date.
Deep Dive
How the Calculations Work
All three modes use the same core arithmetic and run entirely in your browser.
What Makes This Calculator Useful
3 Calculation Modes
Count weeks between dates, find end dates, or find start dates.
Business Weeks
Exclude weekends and count working weeks only.
3 Date Formats
YYYY-MM-DD, MM/DD/YYYY, or DD/MM/YYYY output.
Instant Results
All calculations run in the browser with no delay.
Who Uses It
Who Uses This Calculator
Anyone who plans, schedules, or tracks time by weeks.
Frequently Asked Questions
What are the three calculation modes?
The calculator has three modes. "Calculate Weeks Between Dates" counts how many weeks (and leftover days) fall between a start and end date. "Add Weeks to Start Date" takes a start date plus a number of weeks and returns the resulting end date. "Subtract Weeks from End Date" takes an end date plus a number of weeks and returns the resulting start date.
What does business weeks mode do?
When business weeks mode is on, Saturdays and Sundays are excluded. One business week equals 5 working days (Monday through Friday). This is useful for project timelines, work deadlines, and billing periods where weekends do not count.
How are partial weeks shown in the result?
Results show the number of complete weeks plus any remaining days. For example, a span of 23 calendar days shows as "3 weeks and 2 days" (3 x 7 = 21, remainder 2). For business weeks, the same logic applies using 5-day weeks.
Can I change the date display format?
Yes. Use the Date Format dropdown to choose YYYY-MM-DD (ISO), MM/DD/YYYY (US), or DD/MM/YYYY (European). The format applies to date results shown in the output text. The date input fields always use the browser's native date picker regardless of format.
Can I enter a decimal number of weeks?
Yes. The "Number of Weeks" field accepts decimal values. For example, entering 2.5 weeks in calendar mode adds 17-18 days (2.5 x 7 rounded). This is useful when a project duration is expressed in fractional weeks.
Does the order of start and end date matter for the week count?
No. The calculator uses the absolute difference between the two dates, so the result is the same whether the start date is earlier or later than the end date. You can enter the dates in any order and still get the correct week count.
Ready to Plan by Weeks?
Enter your dates or week count, choose your mode, and get the result instantly.