Desktop Excel on Windows
Open File > Options > General. In When creating new workbooks, select the default font and size, then restart Excel. Microsoft states that the new preference applies to new workbooks, not existing ones.
Review a newly created file rather than expecting an old workbook’s saved cell formatting to change automatically.
Excel on Mac and on the web
On Mac, Microsoft documents Excel > Preferences > General for the default font and size, followed by restarting the app.
Excel for the web provides worksheet font controls rather than the same whole-workbook default setting. Select the intended cells and use their formatting controls.
Review existing worksheets separately
When changing saved cell formatting, compare headings, numbers and any wrapped labels. Different letter widths can affect column fit even if the point size remains the same.
Keep numeric data as numbers rather than replacing digits with decorative Unicode characters to imitate a different font.
Choose a family for the actual task
For aligned character-based layouts, compare the monospaced collection, but judge whether equal widths actually help the worksheet.
Read typeface versus font when specifying a repeatable workbook style for the team.
Your questions, answered.
Will the new default restyle my old workbook?
Microsoft states that the preference applies to newly created workbooks after restart.
Why did column fit change?
A different family can have different letter widths. Review wrapped labels and number display.
Are desktop and web settings identical?
No. The web edition uses worksheet formatting controls rather than the same default-workbook preference.
Sources & background
Sources supporting this page’s explanations. Practical examples are our editorial suggestions.