What is Estimation?
Estimation is a process of calculating quantities and costs of various items required in connection with a work. It is prepared by calculating the quantities from the dimensions on the drawing for various items required to complete the project and multiplied by unit cost of the item concerned.
What is the Purpose of estimation
- To assess the volume of work involved in the project.
- To arrange and organize material, manpower, equipment and tools-and-plant
- necessary for the project. To fix the project completion period.
- To ascertain the fund required for completing the purpose to work.
- To justify the investment from cost benefit ratio.
- To invite tenders and preparation of bill of quantities.
- To obtain necessary administrative approval, necessary technical sanction and arrangement and allocation of funds required for the project.
- For valuation of an existing property.
Types of Estimation
There are five types of estimate:
- Approximate Estimate
- Detailed Estimate
- Quantity Estimate
- Revised Estimate
- Supplementary Estimate e
1). Approximate Estimate:
This is also known as preliminary/rough estimate. This estimate is prepared to work-out an approximate cost of the project in a short period without going into details. This estimate is done for preliminary financial evaluation of different alternatives and for administrative sanctions.
2). Detailed Estimate:
This estimate is prepared by working out the quantities of
different items of work and then working out the cost by multiplying the quantities by
their respective rates. In detailed estimate provisions for any other expenses like.
contingencies, T&P, work-charged establishment etc. are added to the above cost to
calculate the total amount required for project completion.
3). Quantity Estimate:
Quantity Estimate/Quantity Survey is a part of detailed estimate
which list the quantities of all the items required to complete the project. These
quantities are worked out from the drawings. The purpose of Quantity Estimation is to prepare bill of quantities.
4). Revised Estimate:
It is a detailed estimate for the revised quantities or revised rates of items of work originally provided in the estimate without any deviation in original
design and specifications approved for the project. It is required when the material
cost or the material quantities deviates significantly (>5%) from sanctioned value.
5). Supplementary Estimate:
This estimate is worked out during progress of work due to any changes or addition of works to originally approved. A supplementary estimate is different from the revised estimate in the aspect that, the former is worked out for the works which are not present in the original design whereas the latter is worked out when there is a deviation of materials from original proposal.
Abstract Estimate: This is the third and final stage in a detailed estimate. The quantities and rates of each item of work, arrived in the first two stages, are now entered in an abstract form. The total cost of each item of work is now calcula multiplying the quantities and respective rates