Microsoft Project does not have a generic way of displaying week numbers, but some project managers may need to display what week in the year or week of the project a task date corresponds to. What you have to do is create a custom text field then set it to display a formula. I’ve shown before you how to create a custom field but I’ll do this again here.
Displaying Week Numbers using a formula
Creating a Custom Text Field
To create a custom field, right-click on any of the existing column titles in the Gantt Chart grid and choose Custom Fields from the pop-up menu.
Now click on the first available field in the list – here Text1 is selected – and then click on the Rename… button. Give the field a suitable name. here I’ve called it Week Number.
Here is a suggested formula to show the week number relative to the project’s start date:
"Week " & CStr(1+datediff("w",[Project Start],[Start]))
Here is an alternative formula to show the week number in relation to the calendar year of the year the project started:
"Week " & CStr(1+datediff("w",DateSerial(Year([Project Start]),1,1),[Start]))
Of course if you only want the week number and no text before it omit the “Week ” & in the formula.
Having now created the custom field, right-click on the column title where you want to display your new field and select Insert Field from the pop-up menu. Scroll down the list of field names and select your new field. As you renamed a Text field it will still appear with all the other default text fields in the listing so my example above would appear as Text1 (Week Number) in the list.