Take-off calculations: what they must contain and how to set them out

This guide follows French practice: French standards (NF DTU), French regulations and French bill conventions. Most sources are in French.

What take-off calculations are for

The take-off calculations (note de métré, also called the minute; the traditional British equivalent is the dimension sheet) are the document that justifies each quantity: on which drawing, at which location, with which dimensions and which calculation. The summary or the DPGF only give totals; the calculations let you redo them. French training frameworks make this an assessment criterion: the calculations set out on the calculation sheet must be accurate and consistent, and the documents must allow “quick checking and use”.

They have several readers, who are not looking for the same thing:

• the architect or the quantity surveyor, who checks a tender or a valuation and wants to trace a difference line by line;
• the client, who pays for quantities and may ask where they come from;
• the site manager, who orders materials and plans the teams room by room;
• the colleague who takes over the file, and you yourself three months later, when revision C of the drawing arrives.

In a unit-rate contract, where the quantities actually carried out are paid, the calculations also underpin measurement records and interim valuations.

What they must contain

The calculations follow, line after line, the steps of the take-off method: what was read, agreed, measured and calculated.

At the head of the document

• the project, the trade package, the author and the date;
• the drawings used, with their revision;
• the conventions: measuring line, heights, threshold for voids not deducted, rounding rule;
• the assumptions, and any questions still unanswered.

For each item

• the code and description from the form, word for word;
• the location of each line: floor, flat, room, elevation;
• the number of identical parts, then the dimensions;
• the written calculation and its result;
• the deductions, as negative lines, with their own dimensions;
• the quantity of the item and its unit, then the totals carried from one page to the next.

The framework of the French BTS in construction economics adds two useful requirements: calculation details that other colleagues can use, and location drawings showing what has been counted.

Setting them out in columns

The most readable form remains the table, one line per calculation. The marking scheme of a preliminary take-off of floor finishes, published for paper U41 of the French BTS in building economics (2019 session), is a good example: a code per item (10.3.1.1), then, room by room, the dimensions and their product; an « Ens » line totalling the room; « 3f » in front of a line repeated three times; « À déduire » and « Reste » (deduct, remainder) for a shower or a duct; and finally the total of the item with its unit. Its columns can be summed up as follows:

Keep the same unit of length throughout: metres to two decimal places read better than a mix of centimetres and metres.

Writing out deductions

A deduction has its own line, its own name and its own dimensions. Never write a dimension already reduced in your head, such as “4.10” for a 5.00 m wall with a 0.90 m opening: nobody could check it. Three rules:

• An opening is deducted with its own height, not the height of the wall: a 2.05 m door in 2.20 m high wall tiling.
• An opening that is not deducted is written too, marked “not deducted, below the threshold”: the reader knows it was not forgotten.
• The threshold applied is the contract's, stated at the head of the document. There is no universal threshold for voids not deducted.

Rounding: the sum of the lines shown

Take-off calculations are checked with a calculator, by adding up what is written. The safest rule is therefore to round each line once, to the chosen number of decimal places, then to add up the rounded values, as in a DPGF. The BTS marking scheme quoted above does exactly this: the subtotals of its ten rooms, from the bar (26.02 m²) to the second lobby (5.94 m²), add up to exactly 114.78 m².

The other method, calculating the exact total then rounding it, creates visible differences. Three runs of 4.236 m are written 4.24 each: their displayed sum is 12.72, whereas the exact total rounded would give 12.71. The hundredth is negligible; a total that does not match its lines, however, casts doubt on the whole document. Choose a rule, write it at the head and keep to it all the way to the pricing form.

Round results, not dimensions: a dimension read on the drawing is copied exactly as written.

The link with the DPGF, the BPU and the DQE

The take-off calculations feed the contract's pricing form: they must follow its codes, its order and its units.

• Global lump-sum contract. Each total of the calculations is carried to the quantity column of the DPGF, the breakdown of the lump-sum price. If the designer has supplied quantities, the calculations are the tool for checking them before committing.
• Unit-rate contract. The BPU (schedule of unit rates) sets the price of each unit; the DQE (estimated bill of quantities) applies these rates to estimated quantities to compare tenders, without contractual value in principle. During construction, it is the quantities carried out that are paid, and the as-built calculations justify them.

An item whose code or wording changes between the calculations and the form makes the reader search; calculations that follow the form word for word can be checked item by item. These acronyms and the other words of the trade are defined in the take-off glossary.

Example: take-off calculations in columns

Tiling package for two identical flats, A and B, hence the “×2” on every line. Drawings at revision B, dimensions to the finished face. Conventions taken for the example: shower room wall tiling 2.20 m high, shower tray not tiled, all openings deducted, quantities rounded to the hundredth.

Each total is the sum of the partials written above it: 42.64 + 3.24 + 3.84 = 49.72; 9.12 − 1.62 + 2.88 = 10.38; 37.84 − 3.28 = 34.56. These four totals go as they are into the quantity column of the DPGF, against the same codes.

The door is deducted over its 2.05 m height, not over the 2.20 m of wall tiling: deducting it over the full height would remove 2 × 0.80 × 0.15 = 0.24 m² too much.

The most common mistakes

• Dimensions already reduced in the head, impossible to check.
• Lines with no location: the room can no longer be found when the client asks a question.
• Missing units, or a total in m² under lines in ml.
• A total that is not the sum of the lines shown, or different rounding between the calculations and the pricing form.
• Page totals forgotten or carried forward wrongly.
• No drawing revision: at the next revision, impossible to know which lines to revisit.
• Openings not deducted and not mentioned, which the reader takes for omissions.

Doing it in Kotelys

The take-off calculations are a PDF report of the Reports tab, alongside the quantity summary, the annotated drawing set and the Excel workbook. They follow the same order and the same codes as the summary, and write out the calculation of each object drawn.

• A band per type, then a block per object with its reference (“1.2.3-1”), the same on the drawing set and in Excel.
• For an area: the gross, each deduction, the net and the perimeter. For a length: the segments, each opening (“− Opening 1: 1.20 × 1.25”) and, with a height, the wall area; an opening left undeducted is written “not deducted”.
• Written values are rounded, with at least two decimal places in the calculations, and each total is the sum of the lines shown.
• With “Break down by zone”, an object straddling two zones is written under each, with its share.
• Depending on the chosen profile: a cover page, a drawing thumbnail next to each object, a signature block.

Kotelys writes out what you have drawn: the split into items, the heights and the threshold for voids not deducted remain your choices, and the calculations do not replace reading the specification.

Further reading: Kotelys features, including take-off calculations, and the other guides.

Sources

1. Éduscol STI, BTS Études et économie de la construction, 2019 session, paper U41, marking scheme: preliminary take-off of package 10 set out on a calculation sheet
2. Éduscol, Bac Pro Technicien d'études du bâtiment framework: calculation sheets, setting out calculations, measurement records
3. Éduscol STI, BTS Management économique de la construction framework (Official Journal, 31/01/2021): calculation details, location drawings, detailed take-off sheets
4. code-commande-publique.com, « Détail quantitatif estimatif (DQE) »
5. code-commande-publique.com, « Bordereau des prix unitaires (BPU) »: rates applied to the quantities carried out

Thresholds and values described as “taken for the example” are not rules: those of your contract (specification, bill of quantities) always prevail.