Plug Number
A placeholder cost figure inserted in an estimate when actual pricing is not yet available, intended to be replaced before bid submission.
Definition
A plug number is a placeholder cost figure that an estimator inserts into a cost estimate when the actual price for a scope is not yet available. The plug is typically based on historical data, an order-of-magnitude calculation, or an educated guess, and it is meant to be replaced with a real, sourced number before the bid is submitted.
Plug numbers are essential for keeping the estimate moving forward when subcontractor quotes or vendor pricing is still outstanding, but they are dangerous if they are forgotten and submitted as the actual bid number.
How plug number is used in estimating
During the bidding cycle, the estimator works against a deadline and cannot wait for every subcontractor or supplier to return a quote before the larger estimate can take shape. Plug numbers are inserted on lines where pricing is pending, and the estimator continues building up the rest of the bid in parallel. As real quotes arrive, the plugs are replaced one by one. The day before bid, the estimating team should run a "plug audit" to confirm every plug has been replaced.
Disciplined estimating teams flag plug numbers visually in the estimate (color, comment, or a dedicated column) so they cannot be overlooked. They also document the basis for each plug — historical job, RS Means assembly, similar project — so that if a plug becomes the final number it is at least defensible. Submitting a bid with a forgotten plug number can be a project-killer; some of the worst estimating losses in the industry come from a plug that was never replaced.
Managing plug numbers
Always flag plug numbers clearly in the estimate so they cannot be missed. Document the basis (historical, RS Means, parametric) for each plug. Run a final review the day before bid submission to confirm every plug has been replaced or accepted as final. If a plug must remain in the final bid because pricing did not arrive in time, increase the contingency or qualify the bid accordingly. Never let a plug become a final number silently.
Frequently asked questions
Q.What is the difference between a plug number and an allowance?
A plug is an internal placeholder meant to be replaced with a real price before bid. An allowance is a contractually disclosed dollar figure for a scope that has not yet been finalized, with a true-up at completion. Plugs are estimating tools; allowances are contract terms.
Q.When should an estimator use a plug number?
When pricing for a scope is pending and the rest of the estimate cannot wait. Plugs are tools to keep the estimate moving; they are not a substitute for sourced pricing on the final bid.
Q.How do you avoid leaving plugs in a final bid?
Flag plugs visually in the spreadsheet, document each one, and run a final plug audit before submission. Mature estimating teams maintain a plug log alongside the estimate.
Q.Are plugs documented anywhere in the bid documents?
No — plugs are internal to the contractor and never disclosed to the owner. Allowances, by contrast, are explicit in the contract.
Save time with AI-powered estimating
Producing accurate plug number the manual way takes hours. BuildVision AI reads your drawings and generates structured takeoffs, BOQs, and priced bids in minutes.
AI takeoffs
Direct from PDF and BIM drawings, structured by spec section.
BOQ generation
Itemized bills of quantities ready for pricing or owner submission.
Quote and bid
Professional priced quotes and bid packages assembled automatically.
14-day free trial · No credit card required