Weeks Calculator
Calculate weeks between dates, add or subtract weeks from a date, count weeks from today, and convert any date to an ISO week number. The tool runs in your browser and does not require registration.
Weeks between dates
Enter two dates to calculate the exact number of days, full weeks, and remaining days between them.
Add or subtract weeks
Choose a date, enter the number of weeks, and calculate the resulting date while keeping the same weekday.
Weeks from today
Find the date that is a certain number of weeks from today. Use negative numbers to count backwards.
Date to ISO week number
Convert any date into its ISO week number and ISO week-year. This is useful for reporting and scheduling.
How to use the week calculator
Select a calculation type, enter the required dates or number of weeks, and the result appears instantly. The calculator is useful for project timelines, school terms, contracts, travel planning, recurring schedules and countdowns.
Why calculate in weeks?
Weeks are consistent seven-day blocks. That makes them easier to use than months when you need a precise duration. A month can be 28, 29, 30 or 31 days, while a week is always seven days. This is why many teams plan in weekly cycles and why week numbers appear in reports, delivery schedules and academic calendars.
If you are planning something important, write down both the calculated result and the date range. For legal, financial or medical situations, always confirm whether the deadline uses calendar days, business days or inclusive counting.
Calculator FAQ
What week is it today?
Today is in week 18 of 2026.
Are ISO weeks Monday to Sunday?
Yes. ISO weeks start on Monday and end on Sunday.
Is my data sent anywhere?
No. Calculations run in your browser and do not require registration.