Every estimating course at the Institute has one session where the lecturer hands the class the same drawing, asks them to measure the concrete and reinforcement of a single floor, and then compares the answers. The gap between the highest and the lowest figure in the room is usually 15–25% — on one drawing, among people who all hold engineering degrees. That is why quantity take-off is the skill that decides whether someone can work as an estimator, and also the part most often treated as an afterthought.
This article explains what quantity take-off is and where it sits in the estimating process, then sets out a five-step method for measuring off the drawings. The main part is the seven mistakes our lecturers see most often when marking, each with a concrete example. At the end there is a short exercise you can use to test yourself.
What quantity take-off is, and where it sits in estimating
Quantity take-off (also called measurement, or taking off) is the work of reading the design drawings and calculating how much of each item of work has to be carried out: how many m³ of column concrete, how many kg of beam reinforcement, how many m² of slab formwork, how many m² of wall plaster. The output is a quantity schedule — a list of work items with their quantities and the derivation of each figure.
Measuring quantities and looking up the norm code do not have to happen in that order. Some estimators find the norm code first, then measure exactly the way that norm requires. Others measure first and look the code up afterwards. Many do both at once. Any of these works, provided the measured quantity matches the measurement conditions of the norm applied to it.
Whichever order you work in, the quantity remains the number everything rests on, and an error there does not stay there. Whatever the direct cost is out by, that sum is then multiplied again by the percentage-based items that follow: indirect costs, pre-tax profit, and value added tax. A cubic metre of concrete missed in the take-off costs more than a cubic metre of concrete.
Where to start learning construction cost estimating? places this step inside the full learning path, and the Construction Cost Estimating course likewise spends its opening sessions on measurement.
On one project the same quantities are measured several times by different people. The design consultant measures to prepare the estimate; the appraising body measures again to check it; the contractor measures again to bid. Then during construction the QS measures what has actually been built, for payment. At every one of those points the figure has to be traceable back to a drawing — that is what separates a quantity schedule someone can use from one that merely exists.
On the regulatory side, the Ministry of Construction's guidance on measurement sat for several years in Circular 13/2021/TT-BXD. From 1 July 2026 the new cost-management framework (Decree 206/2026/ND-CP, Circulars 36/2026 and 37/2026/TT-BXD) replaces the 2021 set. In it, the determination of quantities is dealt with alongside the estimating method, and taking quantities directly from a BIM model is encouraged. The measurement principles below are professional practice that has survived several changes of regulation; when you prepare a real submission, still check against the documents in force at that time.
How to take off quantities from drawings: a five-step method
Beginners tend to open the drawing and start calculating. Experienced people follow a sequence, and the sequence is what stops them missing things.
Step 1 – Study the documents. Read the whole set — architectural, structural and MEP — together with the specification and the general notes. Understand how the building will be built, what the structural system is, which materials are used, and where the drawings from different disciplines disagree, so you can ask before you measure. Beginners skip this step, and it is the source of most of the errors further down.
Step 2 – Build the list of work items. Write out the items in construction sequence (substructure, superstructure, finishes, external works) and in the way the norms classify them. Column concrete is one item, but it has to be split by grade, by section size or by pouring height if the norms split it that way. Name the items the way the norms name them, so that looking up the code later is not guesswork.
Step 3 – Measure each item. For every item, take the dimensions from the drawing and write down the formula and the location (gridline, floor, member), using the unit the norms use. Write enough derivation that somebody else can check it without asking you.
Step 4 – Total up and cross-check. Add up by item, then compare against rule-of-thumb ratios: kilograms of steel per m³ of concrete for each type of member, m³ of concrete per m² of floor, m² of formwork per m³ of concrete. Anything far from the usual range is where you look again.
Step 5 – Produce the quantity schedule. Present the items, units, quantities and derivations in a consistent format, ready to enter into estimating software or to submit for appraisal.
Seven quantity take-off mistakes beginners make
The list is ordered by how often it comes up when marking students' work at the Institute. Each mistake comes with a shortened example.
1. Double counting or missing material where members meet. Columns, beams and slabs meet at joints; without a clear convention you either count one lump of concrete twice or leave it out. Example: a student measures beams along the gridline length (12 m) having already measured columns over their full height — the length of beam inside the column is counted twice. A common convention is: columns run the full storey height, beams take the clear span between columns, the slab is measured whole and the beam only counts the depth below the slab. What matters is not which convention you pick, but that you use it consistently and write it down.
2. Forgetting deductions, or deducting the wrong things. Masonry measured without deducting door openings, slabs without deducting stair and service voids, plaster without deducting window openings. The opposite happens too: people deduct small openings that the convention says are not deducted. Read the deduction rules for each type of work in the measurement guidance, and note them in the derivation itself.
3. Taking reinforcement from the design schedule without checking it. Bar schedules in design documents very often omit lap lengths, hooks or anchorage, or state the wrong number of bars. The second common steel error is calculating the weight from the wrong diameter or the wrong unit weight. Reinforcement has to be measured from the bar detail drawings: work out the length of each bar type including laps and anchorage, then multiply by the unit weight for that diameter.
4. Wrong unit, or the wrong basis of measurement for the item. Concrete is measured in m³ but formwork in m² of the surface in contact with the concrete; plaster in m² of the plastered face; tiling in m² of the finished face; excavation carries factors for battered sides and bulking. Students often measure beam formwork as the plan area of the beam, when it should be the two sides plus the soffit.
5. Classifying items outside the conditions the norms set. The norms split many items by condition: column section, pouring height, wall thickness, internal or external location. Lumping every column into one line and looking up a single code is wrong at the quantity stage, however correct the arithmetic. This is where reading drawings and understanding the norms have to go together.
6. No derivation, or a derivation nobody can follow. A line reading "Column concrete: 12.5 m³" with no formula is a line the checker will measure again from scratch. A proper derivation records number × length × width × height, plus gridline and floor. The habit also helps you find your own mistakes when you total up.
7. Not cross-checking against ratios. Beginners submit the schedule as soon as the addition is done. Experienced people always look at a few totals: reinforcement in the beams and slabs of an ordinary building falls within a fairly narrow kg/m³ band, and concrete for the whole building within a narrow m³/m² band. When one floor has twice the steel of a comparable floor, there is almost certainly an error back at step 3 — and this is the cheapest way to find it.
What the seven have in common: not one of them is caused by "not knowing the software". All of them come from reading the drawings too quickly, not understanding how the element is built, or having no working convention. That is why How to read construction drawings for beginners comes before every estimating subject in the Institute's learning path, and why people from outside the industry are told to start with the Construction Drawing Reading course rather than with estimating software.
By hand, in software, or from a BIM model
The three are not alternatives so much as different answers to the question of who carries the risk of an error.
| Method | Advantages | Limits | Suits |
|---|---|---|---|
| By hand in Excel, measuring on the CAD drawing | You understand every figure; works with any kind of documentation | Slow; depends on the individual's habits | Learning the trade; small projects; checking a result obtained another way |
| Estimating software (G8, F1, Eta, GXD and others) | Fast entry, automatic norm lookup and pricing, ready-made derivation formats | The software does not measure for you; a wrong quantity still produces a tidy-looking estimate | Once you can measure by hand; regular production work |
| Taken from a BIM model (Revit, Navisworks and others) | Fast, consistent with the design, updates when the model changes; encouraged in the new framework | Only correct if the model is built correctly and completely; many items — formwork, finishes, earthworks — still have to be measured separately | Projects with a model detailed enough; comparing options quickly |
What our lecturers tell beginners: learn to measure by hand first, on at least one complete building. Software and BIM accelerate someone who already knows what they are measuring, and conceal the errors of someone who does not. A person who is solid on measurement picks up model-based take-off very quickly; it does not work the other way round.
An exercise to test yourself
One floor of a reinforced concrete frame. Column grid 4 m × 4 m; the floor plan is 8 m × 12 m (three bays by two), giving 12 columns of 300 × 300 mm. Storey height is 3.6 m from the top of the floor below to the top of the floor above. Beams of 200 × 400 mm run along every gridline; the slab is 100 mm thick. Convention: columns run the full storey height; the slab is measured over the whole plan; the beam counts only the part below the slab, measured over the clear span between columns.
Work out the concrete for columns, beams and slab, then compare:
- Columns: 12 × 0.3 × 0.3 × 3.6 = 3.888 m³.
- Slab: 8 × 12 × 0.1 = 9.6 m³.
- Beams: total length along gridlines = 3 lines × 12 m + 4 lines × 8 m = 68 m. The safest way to remove the part inside the columns is to work span by span: 9 spans in one direction and 8 in the other, each 4 − 0.3 = 3.7 m, giving 17 × 3.7 = 62.9 m. Section below the slab: 0.2 × (0.4 − 0.1) = 0.06 m². Beams = 62.9 × 0.06 = 3.774 m³.
If your beams came to about 5.0 m³, you included the part of the beam that sits inside the slab (mistake 1). If you got 4.08 m³, you forgot to deduct the part inside the columns (mistake 1 again). If you got 3.774 m³ first time, your habits are already better than most beginners'.
The exercise covers concrete only. On the Construction Cost Estimating course, students measure a complete residential building from foundations to finishes, reinforcement and formwork included, with every line corrected by the lecturer. Anyone who wants to go further into measurement for payment on the contractor's side continues with the Quantity Surveyor course.
Frequently asked questions
Are "quantity take-off" and "measurement" the same thing?
Yes. They are two names for the same work. Vietnamese regulations use the term that translates as "measuring quantities"; in the trade people say "taking off" or "measurement".
How long does taking off a five-storey building take?
Someone fluent needs roughly two to four working days for the structure and architecture of a five-storey building with a complete set of drawings. A beginner usually takes three times as long and still needs their work checked. Speed comes after accuracy, not before it.
Can I use the quantities in the tender documents to price my bid?
Measure them again. Tender quantities are there so that bids can be compared, but if you sign a lump-sum contract on quantities that turn out to be short, the shortfall is yours. Experienced contractors always re-measure at least the items that carry most of the value.
Can take-off from Revit replace measuring by hand?
It replaces most of the concrete, steel, walls and doors if the model is built correctly. It does not replace formwork, earthworks, detailed finishes or anything that was never modelled. And you still need someone who understands measurement to check the model.
Do I need AutoCAD to learn quantity take-off?
Enough of it to open a drawing, measure dimensions and read layers and blocks. You do not need to be good at drafting. If the documents are PDFs, the measuring tools in PDF readers also work, though less accurately.