Why does excel seem to struggle computationally (solver, for example) with kind-of big or small numbers?

Answer 1

It can be a number of things. First could simply be the hardware in your computer namely the RAM or CPU (especially the CPU, since this is where the power of the calculations come from).

Next could be that you have Array formulas. You can tell which formulas are an array because they will be surrounded by { } . These tend to be a much more computationally demanding formulas which can weigh down the system as well.

Also depending on which version of excel you have, how you access it (sharepoint, 365 [internet connection]), and even down to how much criteria you have.

It can really be a combination of these things.