The primary objective of Cost Estimating is to support the timely generation of bid or alternative estimates. Cost Estimating also supports management analysis of estimate accuracy, reasonableness and project risk through the generation of summary reports and analysis. Estimates also provide a base of information during construction for such items as scope changes to the contract, variations in costs of the project cost, total project cost, feedback for scheduling etc.
Contruction cost estimating is the process of identifying and compiling the many items of cost that will enter into a construction project. This is a procedure that requires very detailed study of the project during the different construction stages, combined with an intimate knowledge of the availability, characteristics and cost of materials, equipment & labor.

Construction cost estimates becomes. useful for different activities during the construction of the project such as:

1. Procurement - the selection and purchase of materials, equipment & labor for individual work items during construction of the project.
2. Change orders during construcion due to alterations in the original contract, delays in the construction due to unavoidable reasons or any other problems occuring between the Owner and Contractor. Estimating is used to determine the increase or decrease in the amount of the original contract or involve no change.
3. Back charges - charges for materials, equipment & labor or other costs furnished to the Contractor by the Owner, to the Contractor by the Architect / Engineer, or to a Sub-contractor / Vendor by the Contractor due to defective/incomplete or unsatisfactory work during construction. This requires the preparation of an estimated cost of the back charge work so that the Owner or Contractor can have information regarding the dollar amount of back charges.
4. Use of Construction cost estimating becomes helpful in determining the financial position of the project by determining the total cost of work items completed to date, the cost of work required to complete and projected final costs so that one can determine whether there will be a project underrun or overrun.

Also it becomes useful to determine the payment to be made to the Contractor by the Owner for the executed work so that, he has sufficient information concerning the cashflow for the entire project. This also provides relative information to scheduling systems for manpower, planning and resource evaluation.
Estimating also plays an important role in providing information for the cost control of the project. Estimating and cost control are the two most important tasks a Contractor performs to develop equipment & labor production rates for each and every work item of the project during construction and for the selection of labor and equipment. Also estimating becomes useful to keep the cost of an on-going project within the established budget.