Generally, every cell in a row or column has the same size, so you can't adjust the size of a cell individually without affecting the others in its same row or column.

To make all cells the same size in Excel and Google Sheets, select all the columns/row and then click on the Format tool to change the Column width or Row height.

Open the Excel worksheet for which you want to alter the column width. Click on the Home tab in the Excel ribbon. Go to the Cells group and click on the "Format" icon to reveal the Cell Size menu.