Week Number Calculator & ISO 8601 Week Finder
Stay synchronized with global business schedules, manufacturing timelines, and fiscal planning. Find the exact ISO 8601 week number, week boundaries, and year progress.
How to Use Week Number Calculator
Select Date
Choose any past, current, or future date.
Inspect Week Details
View the official ISO week number (W01 to W53) and start/end dates.
Review Year Progress
Inspect total days elapsed and remaining weeks in the calendar year.
About Week Number Calculator
Under ISO 8601, Week 01 of a year is the week containing the first Thursday of January (or the week containing January 4th). Every week begins on Monday.
Supported Formats
Operational Limits
- •Calculations conform strictly to the international ISO 8601 standard (weeks start on Monday).
Key Features
- Official ISO 8601 week numbering standard compliance
- Calculates Monday start and Sunday end dates for the week
- Shows total days passed, days remaining, and percent of year complete
- Identifies 52-week vs 53-week leap calendar years
- Quick jumps to Current Week, Next Week, and Year Milestones
Frequently Asked Questions
Related Tools
More in Date & Time UtilitiesDate Addition & Subtraction Calculator
Add or subtract exact years, months, weeks, days, hours, and minutes to or from any calendar date with business day calculations.
Leap Year Checker
Check whether any year in history or the future is a leap year with Gregorian leap rules explanation and astronomical context.
Day of the Week Calculator
Find the exact day of the week (Monday through Sunday) for any historical or future calendar date with Conway's Doomsday rule.