What is Preliminary or Approximate estimate

This estimate is prepared to decide financial aspect, policy and to give idea of the cost of the proposal to the competent sanctioning authority. It should clearly show the necessity of the proposal and how the cost has been arrived at The calculations for approximate estimate can be done with the following data. The data can be had from a similar construction already complete in the nearby area, executed by the department.
For example: To calculate approximate estimate for a Hospital, per bed cost is calculated from the recent completed hospital and is multiplied with the number of beds required. Similarly for a house, per square meter plinth area is calculated and is multiplied with the proposed covered area. The specifications should also be same. For a road, expenditure of per kilometer length is taken, width also plays the role.
The following documents should be attached with it.
(1) Detailed report
(2) Site plan of the proposal
(3) It should also clearly mention about the acquisition of land, Provision of electric and water supply etc.