Compatibility of Excel files

My computer recently died and I have ordered a new one. I had a number of files which I had created in Excel however I am considering using LibreOffice rather than purchasing Office again. I employ a lot of macros in my worksheets and I was wondering whether they would work in LibreOffice or whether I would have to recreate them. Tfiles in question have an xlsm extension

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Not answering the direct question: why do you talk about “purchasing Office again” after getting a new computer - you should be able to continue using your bought MS Office there?

But wrt compatibility: formula compatibility is generally very good (but still, there’s a range of Excel functions not supported yet in Calc, and Calc functions not present in Excel; also, sometimes functions behave slightly differently, like DAYS); feature support is not so good (in both directions: Calc doesn’t support e.g. dynamic tables; Excel doesn’t support styles); and macro support is very basic (some primitive macros might continue to work, but anything advanced would need a rewrite).

I would consider the question from a financial point of view.

  1. How many different macros do you use in total (if some macros are common to multiple files, count them as 1)? Call this N. Now, let’s assume that 1/3 to 2/3 of the macros will work without issues. Consider one to two hours to fix the issue. So the time (in hours) to fix all the issues is in the range [N / 3, 4 * N / 3]
  2. How much is one hour of your time worth? Call this number M. The cost to fix all the issues is then [N * M / 3, 4 * N * M / 3].
  3. Look at the cost for one MS License. If it is well below this range, buy it!