Are you wanting to compute the cost after the work is complete? Or before it is started as part of a quotation process?

If you are looking at it from the quotation process then the first part is to outline a project schedule. Break it down into enough detail that you feel comfortable with estimating how long each piece will take and what resources are needed for each step. Now look at the schedule and consider what risk there is in each step due to outside factors that you do not control such as, "Will there be a new feature added at last minute?" or "Will the software test platform be available at the right time?" or "Will I need to research some algorithm that is new to me?". Add some time to each step where there is some risk that the step could take longer because of these factors. Next you add together all the time estimates and arrive at the number of time units to do the project, which could be in hours or work-weeks. You determine what it costs to provide human power to work for one time unit plus what ever profit factor you want. Multiply this amount by the number of estimated time units and you get the total labor costs. To this you have to add the costs of the necessary resources. These may include costs for a compiler, a development board, travel costs to customer facility for reviews and project audits, or maybe even the cost of some IP you purchase to simplify the project. Do note that many times the purchase of some IP may make the project more time competitive since it could save many hours of writing it yourself.

Good Luck
Michael Karas