Firstly, you don't calculate at all. You look. You make a test strip. If that doesn't give you enough information, you make another one, and so on. You do as many test strips as are needed. You might need to change grade and make more tests.
It's a good idea to place your test strip so that it shows the effects on the most important part of image. Only you can decide what this is. If you get that right, everything else can be adjusted.
After your test strips have given you a reasonably good idea of exposure and grade, you make a work print. This is not the final ("fine") print, but it does tell you if your previous decisions are right. It should be at the same size and on the same paper as your final print.
If your work print is moderately close to being right, you might then decide to make another work print, perhaps changing the grade or the exposure slightly. This is to be expected, as it will be the first time you have seen the whole image in a print.
Seeing the image as a print might lead you to change the cropping because negatives are hard to judge.
At this point, you may even decide to change your mind altogether about what the print should look like and this will mean beginning at the beginning, with fresh testing.
From the work print you decide on any dodging and burning that's needed. Some workers draw a diagram onto the work print to guide them, if it's complex. You may, for instance, need to hold back one part of the image, and then burn back a small part inside that area. You may not get the dodging and burning right the first time and this is also to be expected.
You may decide that this image needs remedial split-grade printing and this would naturally involve further test-strip making, another work print and perhaps another dodging and burning pattern.
I cannot emphasise enough that printing is not a simply matter of adjusting the highlights or shadows, but of looking at the whole image, and making it the best you can. The only way is to keep on trying and looking with a critical eye until it is right. Lock the darkroom door. It will get easier with practice, but only with practice. A fastidious printer has a full wastepaper bin.
Ian's advice above, although excellent, is for negatives. We almost invariably develop prints for a standard time.