Weeks Calculator
Use five core week tools in one place: convert a date to an ISO week number, turn a week number into a Monday-to-Sunday date range, calculate weeks between dates, add or subtract weeks, and count weeks from today. The tool runs in your browser and does not require registration.
Week number to date
Select an ISO week-year and week number to find the full Monday-to-Sunday week range. The weekday field is optional if you need one exact date inside that week.
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.
Continue with more date tools
Date & Work Calculators
Use separate pages for days between dates, business days, working days and week numbers.
Open →Planning Calculators
Plan deadlines, project timelines, payroll periods, work anniversaries and timesheet weeks.
Open →Week Calendar
Browse ISO weeks by year with Monday-to-Sunday ranges and highlighted current week.
Open →How to use the week calculator
Select one of the five calculation types, enter the required dates, week number 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.
How to convert a week number to dates
Use the Week number to date mode when you already know a week label such as Week 30, 2026 and need the actual calendar dates. Select the ISO week-year, choose the week number, and the calculator returns the full Monday-to-Sunday range.
The weekday dropdown is optional. Leave it on full week range when you need the complete week, or choose Monday, Tuesday, Wednesday, Thursday, Friday, Saturday or Sunday to find one exact date inside that ISO week.
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 24 of 2026.
Are ISO weeks Monday to Sunday?
Yes. ISO weeks start on Monday and end on Sunday.
Can I convert a week number back to dates?
Yes. Use the Week number to date mode, select the ISO year and week number, and the calculator will show the Monday-to-Sunday range.
Is my data sent anywhere?
No. Calculations run in your browser and do not require registration.