Staff Ratio

Hi

I have a lot of staff and customers, each customer is assigned to a category (i.e. Cat 1, Cat 2, Cat 3). and each category has a different weight applied to them in order to calculate a staff members capacity. for example, Cat 1 has a ratio of 1:20 which is 0.05 per customer, Cat 2 has a ratio of 1:6 whcih is 0.16 per customer. 

in excel if i calculate the total of the customers by the multiplier (0.05) and represent it as a percentage then I can display a staff members utilisation. 

however I don't know how to do this calculation in Power BI. 

can anyone help with this?

thanks

Adam