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procurement guide - bills of approximate quantities


Bills of Approximate Quantities are an alternative form of Bills of Quantities (see above) and are prepared early in the design process before a firm design is available.

The contractor is selected, normally by competition from a pre-selected list of between three and six contractors. 

Contractors prepare a tender bid based on pricing a Bill of Approximate Quantities. This is essentially a traditional Bill of Quantities but with the quantities assessed from professional experience by the Quantity Surveyor rather than firmly measured, as would be the case with “Bills of Quantities”.


  • Allows early appointment of a contractor and access to experience in terms of his programming and buildability skills.
  • Enables an earlier start on site to be made than with Traditional Bills of Quantities.
  • Can incorporate Design and Build and Performance Specified works if required.


  • Approximate Bills of Quantities do not establish a firm cost for the work at the time the contractor is appointed, thus there is less price certainty. This is because the actual cost of the works is calculated only when the design is available and detailed re-measurements have been made.
  • The client proceeds to the construction stage at greater risk, despite a check being made at the tender stage by means of bids being submitted by the tendering contractors.


Appropriate for projects for which an early start on site is required or where the design is reasonably well defined or alternatively where the work is of a repetitive nature following on from other similar projects (allowing assessments to be made of the quantity of works from previous experience), but where time is not available for full Bills of Quantities to be prepared.

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