To Aysajan’s answer, I would add that “number of calculations a program needs to run” usually comes from a big-O estimate for the data structures involved, and the size of the data we’re using. So, for instance, if I’m looping over a list with 1k items and doing a thing to each, then that should take ~1k operations. (Really the thing I’m doing to each will probably take more than one operation, but this is a Fermi estimate, so we just need to be within an order of magnitude.) If I’m looping over all pairs of items from two lists, then the number of operations will be the product of their sizes.
To Aysajan’s answer, I would add that “number of calculations a program needs to run” usually comes from a big-O estimate for the data structures involved, and the size of the data we’re using. So, for instance, if I’m looping over a list with 1k items and doing a thing to each, then that should take ~1k operations. (Really the thing I’m doing to each will probably take more than one operation, but this is a Fermi estimate, so we just need to be within an order of magnitude.) If I’m looping over all pairs of items from two lists, then the number of operations will be the product of their sizes.