Week Number Calculator

Find the ISO week number, day of year, and quarter for any date.

ISO Week

Week 22

Day of Year

149

Quarter

Q2

Date Details

ISO Week Number22
Day of Year149 / 365
Days Remaining216
QuarterQ2
Leap YearNo

Use the Week Number Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Our Week Number Calculator helps you pinpoint the ISO week number, day of the year, and the financial quarter for any given date. This is crucial for project management, financial reporting, and scheduling, ensuring consistent tracking across international standards. For instance, knowing that January 1, 2026, falls into ISO Week 1 allows for immediate alignment of annual planning.

The ISO week number adheres to ISO 8601, where Week 1 is the first week with at least four days in the new year, and always begins on a Monday. The day of the year is a simple sequential count from January 1st. Quarters are determined by dividing the year into four three-month periods, with Q1 starting January 1st, Q2 on April 1st, Q3 on July 1st, and Q4 on October 1st.

Be aware that some regional week numbering systems differ from ISO 8601, so always confirm the standard required for your specific application. A common mistake is assuming January 1st is always in Week 1; if January 1st falls on a Friday, Saturday, or Sunday, it will be part of the last week of the previous year under ISO 8601. Double-check your starting date for fiscal years if they don't align with calendar quarters.

Example: Tracking a Project Deadline in 2026

  1. 1 Specific Input: A project deadline is set for March 15, 2026.
  2. 2 Calculation: Using the calculator, March 15, 2026, is identified as ISO Week 11. It's also the 74th day of the year and falls within Q1.
  3. 3 Result: The project deadline is in ISO Week 11, Day 74, of Q1 2026.
  4. 4 Context: This information helps the project manager communicate progress using standardized metrics. If the project's budget is reviewed quarterly, knowing it falls in Q1 is essential for financial reporting, and the ISO week number aids in international team coordination.

Source: TimeAndDate · Last updated: April 2026

Frequently Asked Questions

What week number is it right now?
The calculator shows the current ISO week number, which counts from the first week of January. ISO weeks run Monday to Sunday, and the first week of the year contains the first Thursday of January.
How are ISO week numbers calculated?
ISO 8601 defines week 1 as the week containing the first Thursday of January. Weeks run Monday to Sunday. A year has either 52 or 53 weeks. Some days in early January may belong to the previous year's last week.
What quarter of the year is a given date in?
Q1 is January-March, Q2 is April-June, Q3 is July-September, Q4 is October-December. The calculator shows the quarter along with the week number and day of year.

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