How many calories in 8 slices of bacon?

Depends on the kind of bacon, look on your pack for what a serving size is, then divide the calories in one serving by the number of slices in one serving.

For example

The bacon I eat (turkey btw, that's why the cal count is low) has 2 slices as the serving size, there are 84 calories in one serving so 84/2 = 42 calories in one slice.