The formula
total cost = gross + gross × contributions + costs of the role
Where it comes from
The gross figure in the contract is only the part the employee sees. On top go the employer contributions, a percentage of the gross that varies enormously between countries, and the costs of the role: equipment, licences, training, insurance and space. The sum is what that person's work has to cover.
How to work it out by hand
- Start from the gross annual salary
- Work out the employer contributions as a percentage of the gross
- Add the annual costs of the role
- Divide by the hours actually worked to get the cost per hour
What is worth knowing
The number most used in budgeting is the multiplier: how many times the gross the employee ends up costing. With contributions at 32 % and 3,000 of role costs on a gross of 30,000, the multiplier is 1.42. And the hourly cost has to be worked out on hours actually worked, not on the hours in the year: holidays and public holidays are paid but not worked, so subtracting them makes each useful hour dearer without changing the total cost at all.