When you open a new Excel file, the cells present in front of you have their own default data of width. If you have a certain need and don’t want to adjust the width of each cell one by one, you can change the default width of columns.
Click Home tab, find Format in the Cells section and select Default Width… in the drop-down menu.
Input the width you like and click OK to confirm it.
You can see the width of all the columns have already changed.