What is the major different between Quantity Surveyor & Estimator ?

1quantity surveyor is responsible for all the cost related tasks to the project, the estimator related more specifically to the pre-contract stage in estimating costs for items only and pricing.

Quantity surveyor who is measure the quantity from clear drawing for all stages during project life.

Estimator who is measure quantity from tendering drawing where is not clear or new instruction not appear in drawing but not limit to this determinate.

Estimator: 

• Estimating each and every costs during the tender stage.
• All pre contract activities

Quantity Surveyor:

• All post contract activities.

By the word "Estimator" itself, we can understand that the person employed to measure the quantity or take off from the available drawing/ observed data. 

Quantity Surveyor shall have the vital role for the entire tenure of the project with different responsibilities which include but not limited to, 

Quantity takeoff, Invoicing, Change management, Delay analysis.