Three of Switzerland's employer costs are straightforward matches of what the employee already pays: AHV/IV/EO, ALV, and (under the standard 50/50 model) BVG occupational pension. If you already know an employee's take-home breakdown, you largely already know these three employer-side figures too, they're the same numbers mirrored.
FAK and UVG/BU are different, they never appear on an employee's payslip at all, because they're 100% employer-funded with no employee contribution. FAK funds family and child allowances and is set by canton, not federally, this calculator's default reflects Zurich. UVG/BU covers workplace accidents and is priced by industry risk classification rather than a flat rate.
BVG is also the one line where an employee's age genuinely changes the employer's cost, not just their own deduction. The age-banded contribution structure means an older hire at an identical salary costs more in pension contributions than a younger one, worth factoring into budgeting for senior versus junior roles.