Methods of Taking Out Quantities in Construction

 

In construction, accurate quantity estimation is necessary to figure out how much labor, materials, and money are needed for a project. The process of calculating these values is known as taking out quantities. It is a vital step in preparing detailed estimates, bill of quantities (BOQ), and project planning. A construction estimate's accuracy is largely determined by how precisely quantities are extracted from the drawings and specifications. Depending on the nature and complexity of the project, various approaches are utilized. This write-up discusses the common methods of taking out quantities in construction.

The term "quantity take-off" Quantity take-off is the process of measuring quantities of different construction items such as excavation, concrete, brickwork, plastering, flooring, etc., based on architectural and structural drawings. For the purposes of cost estimation, procurement, and billing, these quantities are recorded methodically. Main Methods of Taking Out Quantities
There are several approaches used to take out quantities, but the three most widely recognized methods are:

1. Center Line Method

Description:
In the case of buildings with uniform cross-sections, the center line method is frequently utilized. To calculate quantities, it involves measuring the wall's total center line length and multiplying it by its breadth and depth. Formula Example:
Quantity equals the centre line's length, width, and depth. Suitable For:
Load-bearing walls
Footings and foundations with same dimensions
RCC beams and slabs in framed structures
Advantages:
Faster and simpler method
eliminates the need to measure each side individually. Minimizes errors in deductions for junctions
Disadvantages:
Less accurate when wall thickness varies
Not suitable for shapes that aren't round. 

2. Long Wall and Short Wall Method
Description:
This traditional method separates walls into long walls and short walls. The long wall is measured from outside to inside, while the short wall is measured from inside to out side from the outer face to the inner face, measure the length of the long walls. Measure the short walls from inner face to inner face.
Multiply each length by the corresponding breadth and depth to get quantities.
Formula Example:
Quantity = Length × Breadth × Depth (for both long and short walls separately)
Appropriate for: Construction made of masonry with distinct long and short walls Advantages:
Detail-oriented and precise for small buildings Suitable for manually preparing estimates
Disadvantages:
Time-consuming
Difficult for irregular layouts
3. Crossing Method
Description:
Internal dimensions are measured and all intersecting (crossing) points are adjusted in the crossing method. This is useful for calculating junctions and overlaps in construction elements like walls and beams.
Steps:
Measure internal lengths
Count all junctions and crossings
Deduct or add accordingly to avoid overestimation or duplication
Suitable For:
Complex floor plans with many wall junctions
structures whose dimensions frequently shift Advantages:
Offers more accuracy in deduction for junctions
Suitable for calculating plaster, painting, etc.
Disadvantages:
Complicated and time-consuming
Not suitable for beginners
Other Methods of Support In addition to the primary strategies described above, the following additional practices assist in more efficiently removing quantities: 

A. Specific Measurement Each item of work (earthwork, concrete, brickwork, etc.) is measured separately based on its location in the plan, elevation, and section.
B. Dimensional Sheet and Abstract Sheet
Dimensional Sheet: A detailed measurement sheet with formulas and units.
These sheets guarantee orderly recording and prevent misunderstandings during billing or tendering. New Techniques for Quantity Take-Off With the development of technology, quantity take-off can now be accomplished with software like: AutoCAD – For measuring dimensions from digital drawings
Revit – For extracting quantities directly from BIM model .Estimating software for digital take offs Bluebeam, PlanSwift, CostX
MS Excel is used for manual organization and calculation. These tools increase speed, accuracy, and reduce human error in quantity estimation.
Conclusion
The construction project's type, complexity, and scale determine the method for removing quantities. The center line method is faster for regular structures, while the long and short wall method is more precise for detailed work. Despite its complexity, the crossing method works well for structures with multiple intersections. Accurate quantity take-off is essential not only for cost estimation but also for procurement planning, budgeting, and execution. Estimators can guarantee cost-effective and efficient construction planning with the right understanding of these techniques and modern tools.