Karyotype asymmetry is well known in karyological studies of plants; however, there is no calculation of karyotype symmetry/asymmetry in other organisms. This study introduces a new formula (S/A(I)) for the measurement of the karyotype symmetry/asymmetry index. The main questions investigated are as follows. (i) Why is the new karyotype symmetry/asymmetry formula necessary? (ii) Which chromosomes are subtelocentric or acrocentric? (iii) What are the limits of symmetry/asymmetry according to the new formula? (iv) Is the human karyotype symmetrical or asymmetrical? In addition, the symmetry/asymmetry index is applied to the species and families of Cetacea as an example.