Hi mocmo
Not sure if this helps answer your question.
When I worked in placing temporary accountants, I always tried to charge the client a rate which specified all the costs e.g.
We will charge you an daily rate of €100
We will charge you the holdiday and other statutory pay which we pay to the employee.
We will charge you employers' prsi of 10.75% of the gross amount.
+ our fee
However, some clients insisted that we charge them a fee per hour worked and this is how I worked it out, if I remember correctly.
€100 per day
= €500 per week
= €26,000 per year
+ 10.75% Prsi = €28,795
Number of days worked
52 weeks x 5 days = 260
Less holidays = 20
Less public holidays = 9
Actual days = 231
Rate per day worked €124.65 + our fee
So you need to up your employee rate by 25%
Of course, you have other costs to consider, such as advertising, insurance, travel, etc.