What Week Is It? Current Week Number
Read the ISO week number, the ISO week-year, and the Monday–Sunday span of any calendar date.
Processed entirely in your browser — nothing you enter here is ever uploaded.
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About this tool
This page opens the week calculator on today's date, so the answer to "what week is it" is on screen the moment the page loads.
Week numbers follow the ISO 8601 standard used across Europe in logistics, payroll and project planning: weeks start on Monday, and week 1 is the one containing the first Thursday of the year — which is why early January dates can still belong to week 52 or 53 of the previous week-year.
The full calculator also takes any other date, shows its week-year and the exact Monday-to-Sunday range, and runs entirely in your browser.
Example. 1 January 2026 is a Thursday and reads Week 1, 2026, spanning Monday 29 December 2025 through Sunday 4 January 2026. 1 January 2021 reads Week 53, 2020.
Limit. The week is the ISO week, Monday through Sunday, with the week-year taken from that week's Thursday. A Sunday-start business calendar is not a mode on this page.