On a construction project the same numbers pass through several documents. Mixing them up leads to disputes: an owner treats an estimate as a price, or a contractor prices a BOQ that was never complete.
At a glance
| Estimate | BOQ (bill of quantities) | Quotation | |
|---|---|---|---|
| Question it answers | Roughly what will this cost? | Exactly what work, in what quantity? | What will you charge me? |
| Usually prepared by | Engineer, architect or owner | Engineer or quantity surveyor | Contractor or supplier |
| Contains | Approximate quantities and rates | Itemised quantities with units; rates left blank for bidders | Items, rates, totals, taxes and terms |
| Binding? | No | Defines scope when part of a contract | An offer that becomes binding when accepted |
| Stage | Planning and budgeting | Tendering | Before award or purchase |
Estimate
An estimate is a forecast. A preliminary estimate might use a cost per square foot; a detailed estimate measures each item of work and applies current rates. Either way, it helps the owner decide whether the project is affordable and sets a budget. Rates and quantities will change as the design develops.
Bill of quantities
A BOQ lists every item of work with a clear description, unit and measured quantity: for example, "brickwork in 1:6 cement mortar in superstructure, 230 mm thick — 42.5 m³". Bidders fill in their rates against the same quantities, so their prices can be compared line by line. A BOQ is only as good as its measurement and descriptions; missing items become disputes and variations later.
Quotation
A quotation is a contractor's or supplier's priced offer. It should state what is included and excluded, rates, taxes, validity period, payment terms and timelines. Once the customer accepts it (ideally in writing), it becomes the basis of the agreement.
How they connect
- The owner or engineer prepares an estimate to set the budget.
- For tendering, the engineer prepares a BOQ from the drawings.
- Contractors return quotations, often by pricing the BOQ.
- The accepted quotation, with the BOQ and drawings, forms the contract.
Good practice
- Write units and item descriptions precisely; "plaster" is not an item, "12 mm cement plaster 1:6 on internal walls" is.
- Keep a quotation's validity short when material prices are moving.
- Record accepted changes in writing as variations to the quotation.
Tools
Quantities for a BOQ come from calculations like concrete and brickwork. Tradespeople can send a clean priced offer with the free quotation tool.
