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Bill of quantities and abstract of cost

Short answer

A Bill of Quantities lists items with description, unit, and quantity, used for tendering. The Abstract of Cost multiplies quantities by rates to give amounts and total cost. The BOQ provides quantities; pricing it yields the abstract. The BOQ may omit rates, while the abstract always includes rates, totals, and contingency/VAT.

Explain Bill of quantities and abstract of cost, and enumerate the relationship and differences between the Bill of quantities and the Abstract of estimated cost.

Bill of quantities (BOQ)

The BOQ lists all items of work with their description, unit and quantity (and, once priced, rate and amount). It is used in tendering and as the basis of the contract and payment.

Abstract of cost (AOC)

The abstract of cost is a summary sheet in which the quantity of each item (from the BOQ or quantity sheet) is multiplied by its rate to obtain the amount; the total of all items, with contingency and taxes, gives the estimated cost of the project.

Relationship

  • Both are built from the same quantity calculation sheets.
  • The BOQ gives quantities; adding rates to the BOQ gives the AOC (a priced BOQ is, in effect, an abstract of cost).
  • The totals of both must agree.

Differences

BasisBill of quantitiesAbstract of cost
ContentItem, unit, quantity (rate optional)Item, quantity, rate, amount
PurposeTender document and contractCost estimate for approval
PreparedBefore tender, for biddersIn the estimate, by the owner
Who pricesBidder fills in the ratesEstimator uses the analysed rates
Shows total costOnly after pricingAlways, with contingency and tax

✓ Answer checked by Claude Opus 5.5 (high effort)

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