Time Frame & Estimate

I am new BI learner and currently studying kimball datawarehouse toolkit. I have question, How can i estimate a time frame and estimate in terms of working hours for Data Warehouse project. I know we have to go through whole Business dimensional lifecycle. Is there any rough formula? For example: If we are developing a datamart for Sales, they have lets say 120 tables in thier sales schema in thier OLTP database. How can i prepare estimate $ and time line for each step in the project?