FAR 52.211-18—Variation in Estimated Quantity.
Plain-English Summary
FAR 52.211-18, Variation in Estimated Quantity, applies to fixed-price construction contracts that include unit-priced items with estimated quantities. The clause addresses what happens when the actual quantity of a unit-priced item differs materially from the estimate, specifically when the variation is more than 15 percent above or below the estimated quantity. It requires an equitable adjustment in contract price, but only for the cost impact caused solely by the portion of the variation outside the 115 percent/85 percent band. The clause also covers schedule relief: if the quantity variation increases the time needed for completion, the contractor may request a time extension, but must do so in writing within 10 days from the beginning of the delay unless the contracting officer allows a later deadline before final settlement. In practice, this clause allocates quantity-risk in construction contracts, gives both parties a defined mechanism for price and time adjustments, and helps prevent disputes when actual field quantities differ from estimates.
Key Rules
Applies to unit-priced construction items
This clause is used in fixed-price construction contracts when the solicitation or contract authorizes variation in the estimated quantity of unit-priced items. It is not a general price-adjustment clause for all contract types; it is tied to estimated quantities in construction work.
15 percent threshold triggers adjustment
An equitable adjustment is available only when the actual quantity varies more than 15 percent above or below the estimated quantity. Variations within the 85 percent to 115 percent range do not trigger this clause’s price-adjustment mechanism.
Adjustment limited to excess variation
Any price adjustment must be based only on the increase or decrease in costs due solely to the quantity variation beyond 115 percent or below 85 percent of the estimate. The clause does not permit a broad re-pricing of the entire item quantity.
Either party may demand adjustment
The clause allows either the Government or the contractor to request an equitable adjustment when the threshold is exceeded. The adjustment is not automatic; it must be demanded and supported by the cost impact of the variation.
Time extension requires written request
If the quantity variation causes additional time to complete the work, the contractor may request a schedule extension in writing. The request must be received by the contracting officer within 10 days from the beginning of the delay, unless the contracting officer grants a longer period before final settlement.
Contracting officer determines extension
After receiving a timely written request, the contracting officer must ascertain the facts and make a judgment-based adjustment to the completion date as justified. The clause gives the contracting officer discretion to determine the amount of time extension warranted by the delay.
Responsibilities
Contracting Officer
Include the clause when prescribed for fixed-price construction contracts with estimated unit-priced items; evaluate requests for equitable adjustment and time extension; ascertain the facts surrounding the quantity variation and delay; determine the justified extension of the completion date; and, where appropriate, allow a longer period for requesting an extension before final settlement.
Contractor
Track actual quantities against estimated quantities; identify when the 15 percent threshold is exceeded; demand an equitable adjustment when entitled; submit a written request for a time extension within 10 days from the beginning of the delay unless a later period is granted; and support the request with facts showing the cost or schedule impact caused solely by the variation.
Agency
Use the clause only in the circumstances prescribed by FAR 11.703(c); ensure solicitations and contracts properly identify estimated unit-priced items; and administer the contract so quantity variations are handled consistently and documented for pricing and schedule decisions.
Practical Implications
Contractors should monitor unit quantities closely during performance, because the right to a time extension can be lost if the written request is late.
The clause does not guarantee payment for all overruns or underruns; only the portion of cost impact caused solely by the variation outside the 15 percent band is compensable.
Both parties should keep detailed quantity records, field measurements, and cost data, since the adjustment depends on proving the actual variation and its direct effect on cost or time.
Contracting officers should distinguish between quantity-driven impacts and other causes of delay or cost growth; only the former are covered by this clause.
A common pitfall is assuming that any large quantity change automatically changes the price of the entire item; the clause limits the adjustment to the incremental effect of the excess variation.
Official Regulatory Text
As prescribed in 11.703 (c) , insert the following clause in solicitations and contracts when a fixed-price construction contract is contemplated that authorizes a variation in the estimated quantity of unit-priced items: Variation in Estimated Quantity (Apr 1984) If the quantity of a unit-priced item in this contract is an estimated quantity and the actual quantity of the unit-priced item varies more than 15 percent above or below the estimated quantity, an equitable adjustment in the contract price shall be made upon demand of either party. The equitable adjustment shall be based upon any increase or decrease in costs due solely to the variation above 115 percent or below 85 percent of the estimated quantity. If the quantity variation is such as to cause an increase in the time necessary for completion, the Contractor may request, in writing, an extension of time, to be received by the Contracting Officer within 10 days from the beginning of the delay, or within such further period as may be granted by the Contracting Officer before the date of final settlement of the contract. Upon the receipt of a written request for an extension, the Contracting Officer shall ascertain the facts and make an adjustment for extending the completion date as, in the judgement of the Contracting Officer, is justified. (End of clause)