The document that turns a design into numbers: what it contains, how the work is measured and where the rates come from.
A bill of quantities is the ordered list of the work items needed to build a scheme, each one with its own quantity and its own unit rate: quantity times rate gives the value of the item, and the sum of the items gives the value of the works. Stop at the quantities and leave the rates out and you have an unpriced bill. The priced bill is the basis of almost everything that follows: project budget, tender, contract, site accounts.
You take the design apart into elementary work items, following the order in which the site will be built: set-up, demolition and excavation, structure, walls, building services, finishes. For each one you look for the matching item in the reference price list — in Italy this is normally the regional price list in force, or a specialist list — which gives the description, the unit of measurement, the unit rate and the labour content. When a work item is not in the price list you build a new rate, justified by a rate analysis.
Every item is quantified with measurements anyone can check, taken from the drawings: the classic format is equal parts × length × width × height (or weight), with deduction lines where they are needed — the openings in a wall, for example. The measurements stay written in the bill, so that anyone can follow them again: that is what separates a professional bill from a lump-sum guess.
Items are grouped into sections (or work categories), which make the bill readable and feed the later interim valuations. Health and safety costs are kept separate and visible: in Italy they are not subject to the tenderer's discount. From the bill you then get the schedule of rates, the labour content and the project budget for the scheme; on Italian public works the whole arrangement follows D.Lgs. 36/2023.
In ComputoLab you switch on the price lists you need for that project, search for an item by code or description (the search runs across every active list at once), enter the measurements line by line with parts, length, width and height, group them into sections and get totals, labour content and health and safety costs worked out for you. The bill comes out as PDF, Word, Excel or in the XPWE exchange format.
Read also: Published price books · Project budget · Labour content
Bills of quantities, site accounts and quotations in one program, offline, on Mac and Windows.
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