Quantity takeoff

A quantity takeoff is the count, made from the drawings of a design, of every item that the design needs: how many bricks, how many square metres of tiles, how many metres of cable, how many cabinets. It is called a takeoff because the quantities are "taken off" the drawings. Contractors, interior designers and equipment installers all make takeoffs, because a price for a job is only as accurate as the count behind it. In India, the priced list of quantities is usually called the bill of quantities, or BOQ.

Here is how it works in general. An estimator, the person who prepares the price, opens the drawings. For each kind of item, the estimator measures what the drawings show. Some items are counted, such as doors, lights or sockets. Some are measured by length, such as pipes and cables. Some are measured by area, such as walls to be plastered and floors to be tiled. Some are measured by volume, such as the concrete in a slab. Each quantity goes into one list, item by item. The estimator adds an allowance for wastage, because some tiles break and some cable is cut off and thrown away. Each line is then multiplied by a rate: the cost of one unit of the material and of the labour to fit it. The total becomes the quote or the bid.

A small calculation shows the idea. A wall 10 metres long and 3 metres high has 30 square metres of surface on each side. If both sides are to be plastered and painted, the takeoff lists 60 square metres of plaster and 60 square metres of paint.

Done by hand, the takeoff for a large building takes an estimator days, and one missed item can wipe out the contractor's profit on the job. Software now does more of the work. With PDF markup for construction, the estimator clicks along a line on the drawing and the software measures its length. Quantity takeoff software uses AI to read the drawings and produce the count in minutes.

Take, for example, a contractor bidding to build a college hostel. Its construction estimating software turns the takeoff into a price for every floor, and the total becomes the bid.

Consider a family ordering a modular kitchen. A home interior design platform counts every cabinet, hinge and laminate sheet in the 3D design, and the quote lists each one.

Say a company is fitting out a training hall. AV design software lists every screen, speaker and metre of cable before the installers arrive.

How is a quantity takeoff different from a cost estimate? The takeoff is only the count. The estimate adds the prices, the labour, the overheads and the profit. And a takeoff from a 2D drawing has to be measured by someone. In BIM (building information modelling), each wall and pipe in the 3D model already carries its own size, so many quantities can be read straight from the model.