Select the column or columns you want to adjust
Double-click the right border of any selected column header
Use the Home tab
Click Format in the Cells group
Select AutoFit Column Width
Select the entire worksheet with Ctrl+A
Double-click any column boundary to auto fit all columns
Use the keyboard shortcut Alt, H, O, I
Drag the column boundary to manually resize if needed
Use AutoFit from the right-click context menu if available