A bill of quantities is a document that lists and measures the work required on a project, item by item, so that every contractor pricing the job prices exactly the same things. It is the foundation of fair tendering in UK construction, and it is also one of the most misunderstood documents in the industry.
This guide explains what a bill of quantities contains, who prepares it and when, how it is structured, how contractors price one, and how it differs from a scope of works.
What a Bill of Quantities Is
A bill of quantities sets out the measured work in a project in a structured list, with quantities but no prices. Each item describes work — for example, a measured area of partition, a length of drainage run, or a count of doors — against which each tendering contractor inserts their own rate and total.
Because every contractor prices the same measured items, the returned tenders can be compared directly. That is the central purpose: it removes the possibility that one bid is cheaper simply because it left something out. It also gives the client a schedule of rates that can be used later to value variations.
A bill of quantities is prepared before tendering, is normally issued as part of the tender package, and becomes a contract document once the job is awarded. That last point matters. Once priced and incorporated, the measured items carry contractual weight, which is why accuracy at preparation stage is not a matter of tidiness.
Who Prepares It and When
On larger projects, the bill is prepared by a quantity surveyor or cost consultant acting for the client. On design-and-build work it is often prepared by the contractor's own commercial team for internal pricing rather than for tender. On smaller projects it may not exist at all, and the equivalent role is played by a schedule of works or a priced scope.
Preparation timing follows the design. A bill cannot be measured from drawings that do not yet exist, so it is normally produced once the design has reached a stage where the work is measurable. Where the design is incomplete, provisional sums are used to cover work that cannot yet be measured precisely — and those sums are a frequent source of later dispute, because two parties can hold very different views about what a provisional sum was meant to cover.
If you are a contractor receiving a bill, read the preliminaries and the preambles before you look at a single rate. They define how the bill is to be read, what measurement rules apply, and what is included in each item. Pricing without reading them is how contractors accidentally include work they had intended to exclude.
How a Bill of Quantities Is Structured
A well-prepared bill follows a consistent structure. It opens with the form of tender and the preamble, which explain the basis of the document. It continues with the preliminaries, covering site management, temporary works, welfare, plant and supervision — the costs of running the job rather than building it.
The measured works follow. In UK practice these are usually grouped elementally in line with NRM1: substructure, superstructure, internal finishes, fittings, services, work to existing buildings, and external works. Within each element, items are further broken down by sub-element and by the trade or material involved.
Each item typically has a description, a unit of measurement, a quantity, a rate and an amount. The unit is critical. A rate per square metre means something very different from a rate per linear metre, and a misread unit is one of the easiest ways to lose money on a tender.
The bill closes with summary pages, and often with a collection of provisional sums, daywork rates and a schedule of rates for items likely to vary during construction.
Priced, Unpriced and Approximate Bills
An unpriced bill is issued at tender with quantities but no rates. A priced bill has been completed by a contractor and returned. An approximate bill is a variant sometimes used where the design is at an early stage, containing approximate quantities that are to be re-measured later — useful for establishing a contract quickly, but a source of commercial risk for the contractor if the re-measurement is not clearly governed by agreed rules.
A bill of approximate quantities is not the same as a firm bill, and treating one as the other is a genuine commercial hazard. If you are pricing approximate quantities, price the measurement risk explicitly rather than hoping it will wash out.
How a Contractor Prices a Bill
Pricing is not simply multiplying quantities by rates. A contractor works through the bill element by element, deciding for each item whether the work is self-delivered or subcontracted, what labour and plant it requires, what the material cost is at current prices, and what allowance is needed for waste, access and programme.
Preliminaries are typically priced as a lump sum or spread across the programme, while the measured works are priced item by item. Overheads and profit are then added at company level, followed by allowances for risk and, where the tender requires it, for inflation on longer programmes.
The mechanics of doing this quickly are the subject of our guide to construction estimating software. The important discipline is the same whether you work on paper or on a platform: keep measured quantities separate from rates, and record the assumptions you made on each unusual item.
Common Problems and How to Handle Them
Missing items are the most common problem. If the design information does not cover something the job plainly needs, the item may not appear in the bill at all. Contractors handle this by pricing the omission as a qualification in the tender, or by including it and noting the deviation — never by staying silent and hoping.
Ambiguous descriptions are the second. Where an item could reasonably be read two ways, ask for clarification during the tender period rather than guessing, because the ambiguity will be resolved against you at valuation stage rather than in your favour.
Unit errors are the third. If a quantity looks implausibly small for the work described, check the unit before assuming the measure is wrong. Bills are prepared by people, and people occasionally transpose numbers.
Finally, watch for items where the quantities are stated as 'nil' or left blank. These often indicate work the designer believed was covered elsewhere, and they are worth a specific query before submission.
Bill of Quantities Versus Scope of Works
The two documents overlap but do different jobs. A bill of quantities is measured and priced item by item, and is designed for tender comparison and valuation. A scope of works describes what is to be done in a form clients and site teams can follow, often with a price built alongside it rather than extracted from a measured list.
For domestic and small commercial work, a priced scope is usually the more useful document, because the client wants to understand the job rather than compare measured items. For larger tendered work, the bill remains the standard. Many firms need both, and modern platforms let the same underlying takeoff produce either output. Our article on the scope of works template sets out the alternative in detail.
Next Steps
If you want to see a measured bill produced from your own drawings, upload one set at my.suddeco.com. Plans start at £49 per month, with tiers at £49, £99, £179 and £349, or £490, £990, £1,790 and £3,490 annually — see pricing. For questions, email [email protected]. Related reading: how takeoffs work.