A Quantity Surveyor (QS) is a construction industry professional with expert knowledge on construction costs and contracts. They are not to be confused with Land Surveyors or Land Survey Engineers. Services provided by a quantity surveyor may include: Cost consulting and Cost estimating.

An Estimate is a calculation of the quantities of various of work and the expenses likely to be incurred there on. The total of these probable expenses to be incurred on the work is known as estimated cost of the work. The estimated cost of a work is a close approximation of its actual cost. The agreement of the estimated cost with the actual cost will depend mainly upon the accurate use of estimation methods and correct visualization of the work as it will be done.

Importance of correct estimating is obvious. Under estimating may result in the client getting an unpleasant shock when tenders are opened and drastically modifying or abandoning the work at that stage over estimating may lose the engineer his client or his job or in any case his confidence.

Estimating is the most important of practical aspects of engineering, and the subject deserves the closest attention of one aspiring to career in the profession. It is a comparatively simple subject to understand; however, as it brings one up against practical work methods and procedures, acknowledge of it cannot be acquired without close application.

Quantity surveyor is professional working within the construction industry concerned with construction. Costs and contracts these are not to be confused with land survey engineers or land surveyors who are engineers. Quantity surveyors not engineers but construction estimation professionals.