Week Number Calculator
Find the ISO week number for any date and convert between dates and week numbers.
About Week Number Calculator
ToolsOfIndia built the Week Number Calculator for project teams and businesses on weekly cycles who want straight answers in plain language. Find the ISO week number for any date and the full date range of any week in a year, which is the shorthand that European and corporate schedules use. The tool follows the ISO 8601 standard, where the week starts Monday and week 1 holds the first Thursday, and it works both ways - date to week number and week number to date range. Indian exporters receiving week-numbered delivery schedules need exactly this translation, and the tool shows the day of the year too. Because it is a pure local calculation, it is instant and private. It is the small translator that weekly-cycle businesses rely on. Time handling is anchored to IST first, with effortless switching to any world zone - a daily reality in India's global work culture. Typical moments to reach for it: matching a week number to a delivery date, finding the date range of a project week, or checking the week number for an invoice date. Small screen or large, the controls stay finger-friendly and the numbers stay readable.
How to Use the Week Number Calculator
- Open the Week Number Calculator tool above — it loads instantly in your browser.
- Enter your values in the input fields provided.
- The result updates immediately — no calculate button needed (or click Calculate where shown).
- Copy or use your result directly. Nothing is stored or sent to any server.
Key Features of Week Number Calculator
- Date to week number
- Week number to dates
- ISO 8601 standard
- Date to ISO week number
- Week number to date range
- Day of year shown
Related Searches for Week Number Calculator
week number • iso week • week calculator • week of year • calendar week • date to week • week number calculator • iso week number • date to week number • week number finder • iso 8601 week • week range calculator — all available free on ToolsOfIndia.com.
Frequently Asked Questions
What is ISO week number?
ISO 8601 defines week numbers where week 1 is the week containing the first Thursday of the year. Weeks start on Monday and are numbered 1-52 or 1-53.
How many weeks in a year?
Most years have 52 weeks (364 days). Leap years and years starting on Thursday have 53 weeks. Our calculator handles all these edge cases.
Why use week numbers?
Week numbers are used in project management, manufacturing schedules, school calendars, payroll periods, and international business for standardized time planning.
What is ISO 8601 week numbering?
Weeks run Monday to Sunday, and week 1 is the week with the first Thursday of the year, the international standard the tool uses.
Why use week numbers at all?
They give a fixed shorthand for schedules, so week 12 of a year means the same date range to everyone following the standard.