Week Number Calculator
Calculate ISO 8601 week number (Week 1 to 53) for any date.
Leap Year & Calendar Calculator
About Week Number Calculator
The ISO 8601 Week Number & Fiscal Week Calculator determines the international standard week number (Week 1 to Week 53), week start/end dates (Monday to Sunday), and remaining weeks in the year for any calendar date.
How to Use Week Number Calculator
Step 1
Pick any date or click "Today".
Step 2
Select week standard (ISO 8601 Monday start or US Sunday start).
Step 3
Review the calculated week number, week date range, and remaining weeks.
Step 4
Click "Copy Week Info".
Practical Use Cases for Week Number Calculator
International Business & Supply Chain Scheduling
Align manufacturing production schedules and shipping deadlines using standardized ISO week numbers (e.g. `2024-W32`).
Corporate Fiscal Week Accounting
Track quarterly performance milestones across standardized 52/53-week fiscal accounting periods.
Input & Output Examples
Calculating ISO Week for August 15, 2024
Date: 2024-08-15
ISO Week: Week 33 of 52 (`2024-W33-4`) | Week Dates: Monday, Aug 12 to Sunday, Aug 18, 2024
Key Features & Performance
- ✓Calculates ISO 8601 Week Number (Week 1 to 53) and Weekday Index (1=Mon to 7=Sun).
- ✓Displays exact Monday start date and Sunday end date for the selected week.
- ✓Supports US Standard (Week starts on Sunday) and ISO Standard (Week starts on Monday).
- ✓100% Client-Side calculation.
- ✓1-Click Copy ISO week string.
Key Terminology & Definitions
ISO 8601 Week Definition
Week 01 of the year is the first week with a majority (4 or more) of its days in the new year, containing the first Thursday of January.
ISO Week-Date Format (`YYYY-Www-D`)
An international standard format where `2024-W33-4` represents Thursday of the 33rd week of 2024.