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Week Number

This calculated column uses a SharePoint formula to calculate the week number of the year for a date. Because it lives in a calculated column, SharePoint fills the value in for every item automatically - no custom development and nothing for your users to type.
Built with
Features
Calculated Column, Date and Time Column
Category
Formulas

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How It Works

  • What it does: Works out which week of the year a date falls in.
  • What you get: A number from 1 to 53 – an early-January date shows 1 or 2.
  • If a value is missing: If Date is blank, the column shows a blank or an error instead of a week number.

Common Use Cases

  • Week-number reporting
  • Production or sprint week tracking
  • Weekly planning grids
  • Filtering by week of the year

Details

  • Formula Type: Calculated Column
  • Formula Category: Dates & Time

Required Columns

Display nameColumn type
DateDate and Time
Week NumberCalculated

Prerequisites

  1. Create the column the formula reads: Date
  2. Add or edit a few items so there is data for the formula to work with

How to Apply the Formula

  1. Add a column, choose More…, then select Calculated (calculation based on other columns)
  2. Set the data type returned from this formula to Number
  3. Paste the formula below into the Formula box
  4. Click OK to create the column

Formula

=ROUNDDOWN(([Date]-DATE(YEAR([Date]),1,1)+WEEKDAY(DATE(YEAR([Date]),1,1)))/7,0)+1

Common Questions About Week Number Formula

What does this formula do?

ISO-ish US week number. It lives in a calculated column, so SharePoint fills the value in automatically for every item.

Which columns do I need to set this up?

You need: Date (Date and Time). The formula reads these to produce its result.

Can I change the formula for my own columns?

Yes. Swap the column names in brackets for your own, and adjust any numbers or text.

If LookBook 365 is code-free and out-of-the-box, why does this example use a formula?

A SharePoint formula is native, declarative configuration, not custom development. It only works with the item’s own fields and simple logic – it cannot run scripts, reach external services, or change other data, and nothing is deployed to your tenant. It keeps working through Microsoft updates. If you would rather not set this up yourself, this is exactly the kind of thing I configure for clients.

Week Number Formula Example
Week Number Formula Example