Estimating

Base Bid

A contractor's firm price for the core scope of work, separate from alternates. The foundation of a competitive bid.

The base bid is the firm fixed price a contractor submits for the core scope of work as defined in the bid documents, excluding alternates. It is the primary number compared across competing bidders. Owners typically award contracts based on the lowest responsive base bid plus any selected alternates.

A defensible base bid covers everything explicitly required by the drawings and specifications, applies the bidder's standard markup, and excludes anything the contractor wants to price separately as an alternate. Bid mistakes that result in a too-low base bid (relative to the contractor's actual cost) are typically not correctable after submission and result in money lost on the project.

Frequently asked questions

What is the difference between a base bid and an alternate?+

The base bid is the firm price for the core scope. Alternates are optional add, deduct, or substitution items priced separately. The contract is awarded for base bid plus owner-selected alternates.

Can I withdraw a base bid after submission?+

Bid withdrawal rules vary by jurisdiction and contract type. Public bids in most states permit withdrawal only on demonstrated material error within a short window after bid opening. Private bids may permit withdrawal before acceptance. Always read the bid instructions.

How does my base bid compare to my competition?+

On public works, bid results are public after opening. On private bids, owners sometimes share results with all bidders, sometimes not. A base bid 5 to 10% below the field is suspicious and may indicate scope omission; 10% above the field typically loses.

Related terms

Bid

A contractor's formal price proposal to perform a defined scope of work, usually in response to a bid invitation.

Alternates

Optional pricing items in a bid that the owner may choose to add, deduct, or substitute after evaluating the base bid.

Estimate

A contractor's informational projection of project cost. Non-binding and revisable; differs from a firm bid.

Scope of Work

The written description of all tasks, materials, and deliverables the contractor agrees to perform on the project.