What Is a Bill of Materials in Construction?
A Bill of Materials, or BOM, is an itemised list of every material and the exact quantity of each one needed to complete a job — timber, fixings, sheet goods, pipe, cable, tiles, concrete, and every other physical input the build requires. It is a supply-side document: its job is to tell whoever is ordering stock exactly what to buy and how much of it, so the site has the right materials on hand at the right time. A BOM is not the same document as a Bill of Quantities, which prices measured work for a client — the BOM only lists materials to procure, with no labour, plant or margin attached.
Key takeaways
- A Bill of Materials (BOM) lists every material and quantity needed to build the job — it is a procurement document, not a pricing document.
- A BOM differs from a Bill of Quantities (BOQ): the BOM lists what to buy, while the BOQ prices measured work items — labour and material combined — for the client.
- A BOM is usually derived from a quantity takeoff, with a wastage allowance added so the ordered quantity matches what the job actually consumes.
- Builders and estimators use a BOM to place supplier orders, compare quotes, and check deliveries against what was actually ordered.
What is a Bill of Materials?
A Bill of Materials is a structured list of every physical material a job needs, with a quantity against each one — so many square metres of plasterboard, so many lineal metres of skirting, so many bags of cement, so many door hinges. It answers a single question: what do we need to buy, and how much of it?
That focus on materials alone is what sets a BOM apart from other estimating documents. It does not price labour, does not include plant hire, and carries no margin — it is purely a supply list, built so whoever is placing supplier orders has one accurate reference instead of re-reading the plans every time stock runs low.
In plain terms
A Bill of Materials is the shopping list for the job — what to order and how much, not what to charge the client.
Bill of Materials vs Bill of Quantities
A BOM and a Bill of Quantities (BOQ) are easy to confuse because both start from the same measured takeoff, but they serve different audiences. The BOM is an internal procurement tool; the BOQ is a priced, client-facing document.
A BOM tells a supplier or site manager what to deliver. A BOQ tells a client what a measured item of work will cost, with labour, material, plant, overheads and margin all built into each rate.
| Bill of Materials | Bill of Quantities | |
|---|---|---|
| Purpose | What to order and how much | What measured work costs the client |
| Contents | Materials and quantities only | Measured items priced with labour, material, plant, margin |
| Includes labour? | No | Yes, built into each rate |
| Typical use | Placing and checking material orders | Pricing and submitting a tender |
How a Bill of Materials drives procurement
A BOM is usually built from a quantity takeoff, with a wastage allowance added on top so the ordered quantity covers offcuts, breakage and handling loss — not just the theoretical finished quantity on the plans.
From there, materials are typically grouped by trade so an order can be split sensibly across suppliers, and each line carries a unit of measure so quotes and deliveries can be checked against it.
- Placing accurate supplier orders in one pass, instead of guessing quantities from the plans on the fly.
- Comparing quotes from multiple suppliers against the same line-by-line quantity list.
- Checking delivery dockets on site against what was actually ordered, catching short deliveries early.
- Flagging long-lead items — steel, custom joinery, specialty fittings — early enough to avoid delaying the program.
How My Trade Hub helps with materials and quantities
My Trade Hub’s automated quantity takeoff measures items directly from your uploaded plans, so the raw quantities behind both your Bill of Quantities and any materials list you build from it come from the same accurate, plan-based source rather than manual scaling.
Your editable rates library sits alongside those quantities, so you can see the material quantities that drive procurement and the fully priced BOQ that goes to the client, without reconciling two disconnected spreadsheets.
Frequently asked questions
What is the difference between a Bill of Materials and a Bill of Quantities?
A Bill of Materials lists the materials and quantities needed to build the job, with no pricing attached — it is a procurement document. A Bill of Quantities prices measured work items for the client, with labour, material, plant, overheads and margin built into each rate.
Does a Bill of Materials include labour costs?
No. A Bill of Materials only lists physical materials and their quantities. Labour is priced separately, typically in a Bill of Quantities, not in the BOM itself.
How is a Bill of Materials created from a takeoff?
It starts with the measured quantities from a quantity takeoff, then a wastage allowance is added per material to cover offcuts and breakage, and the items are grouped by trade so orders can be placed with the right suppliers.
Who uses a Bill of Materials on a construction job?
Builders, site managers and estimators use a BOM to place and check supplier orders. It is mainly an internal and supplier-facing document, unlike a Bill of Quantities, which is usually seen by the client or tender assessor.
Why does a Bill of Materials need a wastage allowance?
Without a wastage allowance, the BOM only lists the theoretical finished quantity from the plans, not what the job actually consumes once offcuts, breakage and handling loss are accounted for. Leaving it out is one of the most common causes of a mid-job material shortfall.
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