Contracts

What is a unit price contract in construction?

A unit price contract sets a price for each unit of work (per cubic yard, per linear foot, per ton) and pays the contractor for the quantities actually installed, instead of a single lump sum.

A contractor and plan reviewer discuss drawings and permit paperwork across an office desk.
Keep plans, permit requirements and approvals together when preparing construction work. AI-generated illustration.

In a unit price contract, the owner provides estimated quantities for each bid item, and the contractor bids a price per unit. The bid total is just a comparison number. What the contractor actually gets paid depends on measured quantities: if the job needs 4,200 cubic yards of excavation instead of the 3,500 in the bid, the contractor is paid for 4,200 at its unit price. Heavy civil, highway, utility, and site work use this format heavily because exact quantities are hard to know before digging.

How it compares with a lump sum

Unit price vs lump sum
FeatureUnit priceLump sum
Price basisRate per unit times actual quantityOne fixed price for the scope
Quantity riskMostly ownerMostly contractor
MeasurementRequired every pay periodUsually percent complete
Good fitEarthwork, paving, utilities, repairsBuildings with complete drawings

See lump sum contract and the guide unit price vs lump sum bidding for more on choosing between them.

Large quantity swings

A unit price usually assumes a certain volume. Fixed costs like mobilization and supervision are spread across those units, so a big drop in quantity can leave the contractor short, and a big increase can over-recover. Many contracts handle this with a variation clause. On federal fixed-price construction contracts, FAR 52.211-18 provides that if the actual quantity of a unit-priced item varies more than 15 percent above or below the estimated quantity, either party can demand an equitable adjustment for the cost change caused by the quantity outside that band. The clause also lets the contractor request more time if the variation extends the work, with the request due within 10 days of the start of the delay unless the contracting officer allows longer. State DOTs and private owners use their own versions with different thresholds, so read the contract.

A worked example

Say a site contractor bids storm pipe at $95 per linear foot on an estimated 2,000 feet, and the owner's quantity turns out high: only 1,500 feet are installed. The contractor is paid 1,500 times $95, or $142,500. But it had spread $20,000 of fixed costs (mobilization, trench box rental minimums, supervision) across the 2,000 feet, or $10 per foot. On 1,500 feet it recovers only $15,000 of those fixed costs, a $5,000 shortfall. A 25 percent underrun is outside a 15 percent band, so under a clause like the federal one, the contractor could seek an adjustment for the costs tied to the units below 85 percent of the estimate.

Common disputes

  1. Measurement. Neat line versus actual, compacted versus loose yards, and who measured. Settle the method in the contract.
  2. Unbalanced bids. Loading price onto items the bidder expects to overrun. Many public owners reserve the right to reject bids they find materially unbalanced.
  3. Work outside any bid item. Extra work that does not fit a unit item needs a change order.
  4. Late quantity tracking. Without daily quantity records, the monthly pay estimate turns into an argument.

Related terms

Unit price work relies on unit cost data, a solid quantity takeoff, and careful progress billing. Smart Business Automator tracks quantities against each bid item so pay estimates and job cost stay in step; see job costing and WIP automation.

Frequently asked questions

Who carries the risk in a unit price contract?

The owner carries most of the quantity risk, because it pays for actual quantities. The contractor carries the risk that its unit prices do not cover its costs.

What is an unbalanced bid?

A bid where some unit prices are inflated and others lowered, so the total looks low but the bidder gains if certain quantities overrun. Public owners may reject bids that are materially unbalanced.

Can unit prices be renegotiated?

Only as the contract allows. Many contracts have a variation clause for large quantity changes, such as the 15 percent band in the federal clause at FAR 52.211-18.

Are unit prices used on building projects?

Sometimes, for items like rock excavation, soil replacement, or repair work where quantities are uncertain, often alongside a lump sum for the rest.

Sources

  1. Acquisition.gov: FAR 52.211-18, Variation in Estimated Quantity
Written and edited by

Maurice Francois writes and edits construction operations guides for Smart Business Automator. More from Maurice on the Scaling Legends podcast.

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