In Germany the employer is responsible for paying into the social security system The total payment is 40% of the salary and has to be transferred completely to the public health insurance. Half of it (20%) is deducted from the salary. So as total wage cost you can roughly calculate 120% of the gross salary.
In certain cases (expats and other short time visits) no German social security need to be paid due to social security agreements with other countries.
If you also speak German please find further interesting tax topics on my German homepage by clicking here.
Please contact me if I may give you further explanations.