If your client is the owner of the project, then the fees are calculated as a percentage of the total cost of the project. These fees depend on the size and complexity of the project and may range between (1.5%-4% Design, and 1.5%-3% supervision)for the complete package.
However, if your client is a local consultant in Saudi Arabia, then these fees quite less and you can calculate them based on either man-hours or just a lump-sum figure.