M1 Mac Excel file large and extremely slow on MacBook Pro with M1 - solved

I have had a problem for over a year, I have an M1 MacBook Pro and I program many Excel files which each continue hundreds of formulas. After I bought my M1, I noticed that the Mac was taking a very long time to open , save, and to even scroll through those files.

I saw many other M1 Mac user posted about this issue online in Apple Community and also in Microsoft over a year ago- but those threads were all locked- there were many unsuccessful resolution replies and

Anyway - I FOUND A FIX !!!! and I am so happy, I wanted to post it for others to see

Here is what you do with that large excel file that runs too slowly on the M1 mac

1) Duplicate the file (just to be safe)

2) Open the file or the copy, (maybe get a cup of coffee as you wait)

3) Now- Save the Excel file ---> Save As "Excel 2004 xml Spreadsheet"

(When I did that - my file went from 55 MB to 45 kb !!!!! it opens great now

4) Close and reopen the Excel 2004 file. (hopefully you will see it has a smaller memory)

I found this small issue---- all the text in my file changed to colorless- (the file appeared empty)

So..

5) Select all cells, change the text color to black

(I did this and all the formulas, text etc appeared !!)

6) Then when you are satisfied, save it again as the updated Excel version

(I was able to save mine as .xlsb because many online claimed that could help, and that file works for my purposes. BUT even if I save the file without the bin format it still works great

Also, I did not mention (when I found the colorless text , in my case I had to do a bit more work because my file had texts of different colors, red black green blue - so it took me just a while longer to set the text right- but none of the formulas or text were incorrect, all was good. And some graphic shapes that I drew were also colorless - in my case I had so few that I just redrew them - but with time I noticed I could have selected all those and reconfigured their colors weights etc...

Finally, as I made the small corrections in colors, & shapes, I continuously saved , closed, and reopened the Excel file- just to make sure that the file stayed small and that this wasn't just too good to be true.

So... all is well for me! I truly hope this will help someone, I love my M1 Mac and now the Excel files are running great. I guess Microsoft will eventually address whatever the underlying issue is, but its great that I can now use their great Excel product again on an Apple computer.