BOQ vs bill of materials: what is the difference?
A bill of quantities (BOQ) lists measured items of construction work, each with a unit and quantity, for contractors to price into a tender sum. A bill of materials (BOM) lists the parts and materials needed to make one product, with the quantity of each per unit built. One prices work; the other drives manufacturing.
By BOQ Estimator. Published .
Two lists with quantities, and two different jobs
Both documents list things with quantities, which is why they get mixed up. The difference is what the quantity means. In a BOQ it is the amount of work in this project, measured from the drawings. In a BOM it is the amount of a part in one finished product, which production then multiplies by the number of units to be built.
Estimators meet both. A tender BOQ may include equipment priced from a supplier's BOM, and an industrial or services package may arrive as a materials list, often called a material take-off, with the installation still to be priced. For the other common mix-up, see BOQ vs schedule of rates.
Titles are not a reliable guide. A document headed bill of quantities can be a materials list, and one headed bill of materials can carry installation lines. Judge it by its columns and by what its quantities multiply. If you cannot tell, ask in writing which quantities are to be relied on and what the price is to cover.
Checklist
How to tell which document you are holding
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Look at the columns
A BOQ has an item reference, description, unit, quantity, rate and amount. A BOM usually has a part number, description, quantity per assembly and unit of measure, often with a revision and a supplier or make-or-buy flag.
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Check how the list is organised
A BOQ is grouped by bill, section or trade, in the order of the work. A BOM is grouped by assembly: a top-level product with sub-assemblies and parts beneath it, sometimes many levels deep.
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Ask what the quantity multiplies
A BOQ quantity is the whole project's amount, and your rate multiplies it. A BOM quantity is per one parent unit, and the production run multiplies it again.
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Look for prices
A BOQ rate normally bundles labour, plant, materials, overheads and profit. A BOM carries a cost per part, and labour and overhead usually come from separate cost data.
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Treat a mixed pack as two documents
If a bill item says supply and fix for equipment described in a supplier's BOM, price the BOM as the supply cost inside the item, then add handling, installation, plant and testing.
Side by side
A construction BOQ and a manufacturing BOM compared
| Point | Construction BOQ | Manufacturing BOM |
|---|---|---|
| Purpose | Prices a defined scope of work for a tender and values it afterwards. | Defines what goes into a product, for purchasing, planning and costing. |
| Prepared by | Quantity surveyor or cost consultant, usually for the client. | Design or manufacturing engineering. |
| Structure | Bills and sections by trade or element. | Assemblies, sub-assemblies and parts. |
| Quantity means | Measured amount of work in this project. | Amount per one parent unit, multiplied by the build quantity. |
| Typical units | m, m², m³, nr, item, sum. | Each, kg, m, litre, set. |
| Price basis | One rate per unit covering labour, plant, materials and margin. | A cost per part, with labour and overhead added separately. |
| Changes | Addenda before award; variations after. | Revisions and engineering change orders. |
Watch for
What goes wrong when the two are confused
- A BOM quantity priced as a project quantity. A part used four times per unit is not four in total if the project builds twelve units.
- Installation lost inside a supply price. A supplier's list prices the goods. Unloading, positioning, fixing, connecting and testing are still yours to price.
- Units that do not line up. A BOM may count each where the bill measures m or m². Convert before you compare.
- A materials list read as the full scope. A take-off lists what is needed, not the work described in the bill, such as making good or commissioning.
- Revisions drifting apart. BOM revisions and bill addenda move separately. Record which version each price was built on.
- Waste allowed twice, or not at all. Bill quantities are normally net, so waste sits in your rate. A BOM may list net quantities or may include a scrap allowance. Find out which before you add waste.
The tool
How BOQ Estimator helps
BOQ Estimator is built for the Bill of Quantities side. It reads item, description, unit, quantity, rate and amount, keeps item numbers as printed and checks printed subtotals against the items above them. It does not read assemblies or part hierarchies, so it is not a BOM tool. Try it on the BOQ to Excel converter. Free: 1 file per day, up to 10 pages, no account. Files over 10 pages are converted up to page 10 on the free allowance; a page code converts the whole file, up to 150 pages. See plans and limits.
Related
Related guides
FAQ
Questions estimators ask
What is the difference between a BOQ and a BOM?
A BOQ lists measured work in a construction project so contractors can price it. A BOM lists the parts and materials in a manufactured product, with the quantity of each per unit. The first drives a tender price; the second drives purchasing and production.
What does BOQ stand for?
Bill of quantities, sometimes written BoQ. It is the priced or unpriced list of work items, with units and quantities, issued with a construction tender.
Do BOQs include materials?
Only inside the rate. A BOQ item normally has one rate covering materials, labour, plant, overheads and profit, so the bill does not list materials separately. Check the item description and preambles for anything supplied by others.
What is a material take-off?
A list of materials and quantities taken from drawings or a model, used for ordering and pricing. It is closer to a BOM than a BOQ, because it does not describe the work to fix, test or finish the materials.
Can I build a BOQ from a BOM?
Only partly. A BOM gives the quantities of parts, which can feed the supply element of an item rate. The BOQ still needs the work described and measured, such as installation, builder's work and commissioning.
Which one do contractors price a tender from?
Normally the BOQ. Where a client issues only a materials list, ask whether its quantities are to be relied on and how the work is to be priced, and keep the written reply.
Can BOQ Estimator convert a bill of materials?
No. It is built for Bills of Quantities and checks their sections and subtotals. A BOM has a different structure, with assemblies and part numbers rather than bills and collection pages.