What Is a Bill of Quantities (BOQ)?

A complete BOQ captures far more than the obvious trade materials. Every measured item is described precisely enough that any competent estimator would price it the same way, alongside its unit, quantity, and columns for the rate and the extended amount. A typical BOQ contains:

• Measured trade items — such as cubic metres of concrete, square metres of formwork or brickwork, lineal metres of pipe, or tonnes of reinforcement.
• Preliminaries — the project-wide costs of running the site, kept as a separate section (covered below).
• Provisional sums — allowances for work that is not yet fully designed or specified.
• Prime cost (PC) items — allowances for products the client has not yet selected, such as tapware or tiles.
• Dayworks and contingency schedules — a basis for pricing ad-hoc or unforeseen work.

A BOQ is normally organised into sections that mirror how the job is actually built, so each trade can price its own portion and the client can see where the money goes. The measurement follows a recognised standard method, so the same item is described and measured the same way from one BOQ to the next. The main groupings are:

• Preliminaries — supervision, site sheds and amenities, scaffolding and access, temporary services, insurances and cleaning. These are project-wide and not tied to any single trade.
• Trade or elemental sections — grouped by trade (excavation, concrete, brickwork, carpentry, services) or by building element (substructure, superstructure, finishes).
• Provisional and PC sums — collected together so the client can see exactly which parts of the price are allowances rather than firm, measured quantities.

The BOQ is the great leveller of competitive tendering. Because the client — or their quantity surveyor — issues the same measured quantities to every tenderer, each contractor supplies only the rates. The bids therefore differ on price and approach, not on how much work each contractor thought was involved.

This does two valuable things. It makes bids directly comparable line by line, and it exposes where a low bid is really coming from — a genuinely keen rate, an omission, or a pricing error. An assessor can compare rates item by item to sanity-check an unusually high or low total.

Because the quantities belong to the client, the risk of a quantity error generally sits with the client rather than the contractor. That allocation of risk is one reason BOQs remain common on larger and public-sector projects.

A priced BOQ keeps earning its keep long after the tender is won. It becomes the reference document for valuing the job as it progresses, which is why getting it right at tender stage pays off for the life of the project.

• Progress claims — the value of work completed each period is measured against the BOQ rates, so payments track real progress.
• Variations — when the scope changes, the BOQ rates give a fair, pre-agreed basis for pricing the added or omitted work.
• Cost control and forecasting — comparing actual costs against the priced BOQ shows, section by section, where a job is making or losing money.

Traditionally, a quantity surveyor (QS) prepares the BOQ on the client’s behalf, measuring the works from the drawings to a recognised standard method of measurement so the document is consistent and defensible.

On smaller and mid-sized jobs, though, builders and estimators increasingly prepare their own BOQ as part of pricing a tender — either by hand or, more often now, with takeoff software that measures quantities directly from the plans. My Trade Hub automates that takeoff, so an estimator can produce a measured, structured BOQ in a fraction of the time it takes to scale drawings by hand.

It is easy to confuse a BOQ with the other documents in a tender pack. The difference comes down to what each one actually fixes:

• BOQ vs estimate — a BOQ lists measured quantities to be priced; an estimate is the priced prediction of total cost. A priced BOQ is one way to build an estimate.
• BOQ vs schedule of rates — a schedule of rates lists agreed rates without firm quantities, used where the amount of work is not yet known. A BOQ carries measured quantities.
• BOQ vs scope of works — a scope of works describes in words what work is included; a BOQ measures and quantifies that scope so it can be priced.

Most BOQ problems are avoidable and come down to a handful of recurring slips:

• Pricing a rate against the wrong unit — for example per lineal metre instead of per square metre — which can quietly distort a whole section.
• Under-pricing preliminaries because they are easy to overlook next to the more obvious trade quantities.
• Leaving provisional and PC sums vague, so the final reconciliation turns into a dispute over what the allowance was meant to cover.
• Not checking the quantities against the latest drawings — an out-of-date BOQ prices the wrong job.