What is estimation ? What are the type and purpose of estimate?

Engineering Estimating

Today in this post you will find out information about Engineering Estimating. The types of estimates and their purpose of estimation. I hope this article is very helpful to you in estimating information. Read this post till the end of the page. so let’s get started:

You are an engineer, estimator, contractor. This is the most important part of the engineering sector. Without an estimate, the construction cannot possible in the different categories. Like cost, time period, required engineering materials, required labor, etc. This is the pre-planning of construction Technology. Engineer, contractor, the estimator can perform estimates of any construction. 



This performs before the construction. By the estimate gives the value of the cost of construction, the number of members required for the construction, type of engineering materials, the time period for completion of the project.


I will talk about the following topics in this article:
  1. Definition of is estimating?
  2. The type of estimating?
  3. Purpose of estimating?

What is estimation?

An estimate is a record of the materials, items of work, cost of the project, number of labor, time period, and expenditure likely to be incurred in the construction of building, highway, road, dam, boundary wall, irrigation, etc. The estimate gives the probable cost of work. It is determined by theoretical calculations based on plans, drawings, and current rates.

What is the purpose of an estimation?

Estimating is done for more purposes in every engineering field. Following are the main purpose of estimating:
  1. To know the probable cost of the project or work.
  2. Know the approximate quantity of the material and labor required for the project. 
  3. Have an idea about the time of completion of the project. 
  4. To help control the expenditure during execution. 
  5. Support to check the work done by contractors. 
  6. Inviting tenders and arranging contracts.
  7. For technical sanction of the project. 
  8. To help in help fixing standard rent, the sale price of flats, and valuation of properties. 
  9. Collect necessary tools and plants as per the schedule of the project is required numbers. 
  10. Create a schedule of work.
  11. To justify the cost-benefit ratio.



What are the types of estimation?

The followings are the various estimating types. Which list below with details:

  1. Preliminary estimate or approximate estimate or rough estimate. 
  2. Plinth area estimate.
  3. Cube rate estimate or cubical content estimate. 
  4. Approximate quantity method estimate. 
  5. Detail estimate or item rate estimates. 
  6. Revised estimate.
  7. Supplementary estimate. 
  8. Supplementary and revised estimate.
  9. Complete estimate. 
  10. Annual maintenance or repair estimate. 



Preliminary estimate 

This estimate is prepared in different ways for different structures as follows:


Per unit basis: per student for schools and hostels per classroom for schools, per bed for hospitals, per seat for cinema & theatre halls, etc.
Plinth area basis.
Cubic content basis.

Approx. Quantity method. 



Road and Highway:– per Km basis depending upon nature of the road, width, and thickness of metal.
Irrigation channels:
  • Per km basis. 
  • Per hector basis (area of land commanded)
  • Bridge and culvert:- Per running meter of span depending upon the type of structure, type, and depth of foundation. 
  • Sewage and water supply project:
  • Per head of population served.
  • Per hectare basis (area covered)


Plinth area estimate 

This is an approximate method of estimate:

In this method of the estimate, the plinth area of the building calculates for the plinth area estimate. 

The external dimensions of the building floor level take to find out the plinth area. 

Courtyard and other open should not include.

For multi-story buildings plinth area for each story determine separately. 

Approximate total plinth area may calculate by adding 30 % to 40 % of the already calculated building having the same specification as the previously constructed building having the same specification and locality.

The cost of the new building finds out in this method of estimate with multiply the plinth area by the respective rate item of the project.

Rate= cost of construction/plinth area.

The Cost of new building = plinth area * Rate of items of the project.

Cube rate estimate:

A cube rate estimate is also an approximate estimate. 

The cubical content of the building is determined by multiplying the length of breadth and height of the building. 

Floor level to top level of floor height should take to find out the cube.

For a multi-story building, height takes from floor level of one story to top of next higher floor.

The cube rate estimate is more accurate as compared to the plinth area estimate.

Approximate quantity estimate method 

The total length of the walls is found out.

To find a running meter rate of foundation, approx. Quantities of different items calculate per the running meter of the project. 

Similarly for superstructure approx. Quantities of brickwork on the wall, top roof, flooring, etc. Is calculated per running meter.


Supplementary estimate 

It is the type of detail estimate when additional work is to do in the project and then the supplementary estimate do in the original estimate document. 

It requires when further development of the project requirements during the progress of work or project. 

In this type of estimate, the amount of the original estimate and the final estimate is a category in two-part. Like abstract amount should include in the original estimate and the supplementary amount included in the final estimate.

The original estimate was called an obstruct amount. 

Obstruct amount + supplementary amount = final amount of project.

The supplementary and revised estimate 

When work is partially abandoned and the estimated cost of the remaining work is less than 95% of the original sanctioned estimate. 

It is done when there are material deviations or fluctuations and changes in the design properties. 

If at any time before or during the execution of the work, it is found that the original estimate is excessive then the divisional officer may sanction a revised estimate of reducing the amount.

Detailed estimate

It is an accurate type of estimate. Which prepare by working out quantities of every item of work. In this estimate, the individual items are included in the detailed estimate. This includes the detailed particulars items for the quantities, rates, and costs of all the items included for satisfactory completion of the project or work.

In the detailed estimate, the quantities of all items of the project calculate from the respective dimension of the design drawing on a measurement sheet. After complete the quantities of all items then simply multiply by the respective rate of an item of work to found the cost of the item. This is the best and most accurate estimate that can prepare a detailed estimate. 


A detailed estimate is complete by the following topic:

  • Report
  • Specification 
  • Detailed drawings showing plan, section, elevation, side view, and key and index plan
  • Design data and calculations 
  • Basic respective rates adopted in the estimate 
  • It is prepared in two stages:
  • Details of measurement and calculation of quantities. 
  • Abstract of estimate cost 3% to 5% of the estimated cost add to cover miscellaneous expenditure. 
  • A detailed estimate prepares to work-wise.
  • A detailed estimate prepares for sanction, for arranging the contract, and for the execution of the project. 



Complete estimate

This is an estimated cost of all items related to the work in addition to the main contractor to the detailed estimate. 
Following are the point which includes in the complete estimate:

Cost of land 

The actual cost of land 
Cost of surveying 
Prise of examination of deeds.
Defaulting taxes of land, street development if any.
  1. Cost of legal expenses required between an owner and the contractor. 
  2. Cost of main contract or material, labor, and Suspension. 
  3. Contingency 5% of the work or extra work.

Engineering fee

  1. Cost of preparation of plan, design, and estimate. 
  2. Cost of supervision work.
Permit fees for water and electricity during construction. 
Miscellaneous cost of transportation with party and owner.

Annual maintenance or repair estimate 

It prepares to maintain any structure or project in proper order and safe condition.
For building works like whitewashing, painting, minor repairs, etc.
For road works, an annual repair estimate provides for patch repairing, repairs of bridge and culvert, etc.


During the preparation of the estimate, there are unforeseen expenses of a miscellaneous character that cannot reasonably predict. Such unforeseen or incidental expenses are known as contingencies. 
Contingencies amount = 3% to 5% of the estimated cost of the project. 
If the contingency fund is not sufficient then a supplementary estimate or revise estimate must carry out.

Administrative approval 

For any work or project required by a department, approval or sanction of the competent authority of the department concerning the cost and work is necessary at the first instance, which is known as administrative approval.
By the engineering department authorizes can approval to take up the project.




Sanction = To Give official permission or approval for action on any project or work.
Expenditure = the action of spending funds.




After visit this article you get the information about the estimation. I hope you understand the purpose and type of estimate in this article.  If this article is helpful for you to have any doubt please comment me.


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