Engineer's estimate: 3 checks before comparing bids

Key takeaways

• Match bid items, quantities, and measurement units before comparing prices.
• Check price dates and the items covered by adjustment clauses.
• Separate risk allowances from costs already covered by the contract.

Why the engineer's estimate is worth checking

When a state transportation agency advertises a federal-aid highway project, it prepares an engineer's estimate before bids are opened. That estimate is the agency's own view of what the work should cost. Bidders build their prices from their own takeoffs, labor and equipment rates, and supplier quotes. Estimators and owners often want to know how their price compares with the agency's number, and whether a difference signals a problem.

A gap is not proof of a mistake. Estimates and bids rest on different assumptions, schedules, and views of risk. A large or unexplained gap is still a good reason to look more closely before deciding what it means.

The three checks below cover scope, timing and price adjustments, and risk. Owners who are not estimators can use the same checks to ask better questions of the people who prepared the bid. This is general guidance, not legal advice, and it does not replace the contract documents or your agency's procedures.

The main reference is the FHWA guidance on preparing engineer's estimates, bid reviews, and evaluation. Read it first, because it sets the frame for everything that follows. Confirm that you have the current version. The page states that it replaces the Guidelines on Preparing Engineer's Estimate, Bid Reviews and Evaluation, dated January 20, 2004. Older copies in project files or training binders should be checked against the current page before anyone relies on them.

First check: confirm the estimate covers the same work

Before you look at any unit price, confirm that you are comparing the same thing. The answer shapes how you read every number that follows.

The FHWA guidance says the procedures must support full and open competition by ensuring fairness in the pre-bid solicitation process and post award review of construction bids, and it cites 23 CFR 635.110(b) as the basis for that requirement. The estimate is therefore a tool for reviewing bids fairly. Keeping that purpose in mind helps you avoid treating every gap as a sign of cheating, and it keeps you from treating the estimate as the correct price without asking how it was built.

Practical steps for this check include the following.

• Pull the bid documents, plans, and specifications that were in force when bids were prepared. An estimate built on a different scope is not a fair comparison, however carefully its numbers were checked.
• Line up the bid items one at a time. Confirm that descriptions, units of measure, and quantities match. A single mismatched line can explain much of a total gap, and it is easy to miss when you compare only totals.
• Note every change to the bid documents. These changes can affect quantities, scope, schedule, or special requirements after the estimate was prepared, so a project number alone does not guarantee that two documents describe the same work.
• Identify items that were excluded, deferred, or handled as allowances in one document but not the other. A provisional sum that appears only in the bid can make two numbers look far apart even when the underlying work matches.

Quantities deserve particular attention. Bid quantities come from the bid schedule, while your own takeoff may reflect how you plan to sequence or measure the work. If your takeoff uses a different measurement basis than the pay item, convert it before comparing. A difference that looks like a pricing gap is often just a measurement difference. For that step, use the guide to converting takeoff units.

When the scope lines up, move on. When it does not, write down each mismatch and note which ones affect the outcome. A scope difference often reappears as a timing or risk difference, so these notes will help in the later checks. A good test is whether someone outside both teams could read your notes and reach the same conclusion about scope. If they could not, the notes need more detail.

Second check: test the timing and price adjustment assumptions

The second check concerns time. Federal-aid projects can run for months or years between bid opening and completion, and the cost of materials, fuel, and labor can move during that period. An estimate priced on one set of prices and a bid priced on another will differ for reasons unrelated to how well either party understood the work.

Price adjustment clauses are one way agencies manage this exposure. The FHWA guidance points to the AASHTO Committee on Construction's 2019 Survey on the Use of Price Adjustment Clauses for Inflation as the most recent summary of practices in states.

The same guidance refers to FHWA Technical Advisory TA 5080.3 for additional guidance on the use of price adjustment clauses. Read the advisory for the federal view, and read your project's own provisions for the terms that actually apply to your contract.

For inflation in the estimate itself, the guidance points to Chapter 6 of the AASHTO Practical Guide to Cost Estimating, which is titled Inflationary Considerations. Use that reference when reviewing the estimate's inflation assumptions.

When you read an adjustment clause, identify four things: the items it covers, the index or source used to measure change, the base period, and the timing of any adjustment. Each one can change the result. Two clauses that look similar on different projects can produce very different outcomes if any of these details differ. The guide to escalation clause contract checks can help organize that review.

When you test the timing and adjustment assumptions in a comparison, ask the following questions.

• What date is the estimate priced to? If the estimate reflects earlier prices than your bid, part of the gap may simply be timing. You need both dates before you can judge the rest.
• Does this project have a price adjustment clause at all, and what does it cover? Read the contract language itself, not a summary, because summaries often leave out conditions that change the answer.
• If the estimate assumed little escalation and the clause covers only some items, your bid may carry risk on the uncovered items that the estimate did not price. That is a legitimate difference in assumptions, not an error by either side.
• If your bid added escalation to materials that the clause already adjusts, you may be pricing the same risk twice. This is a common source of an unexplained premium, and it is usually easy to correct once you see it.
• Are you using the same kind of escalation source as the agency? Different indexes, geographic areas, or periods can make a comparison unfair even when the arithmetic is correct.

Keep this question separate from the question of efficiency. A clause changes who carries cost exposure. It does not, by itself, tell you whether a bid is high or low. Two bids with the same exposure can still differ because one contractor assumed more productive crews or better purchasing terms. Those are real differences, but they belong to a different discussion, and mixing the two makes both harder to evaluate.

Write your answers in plain language. A sentence such as "the estimate used earlier prices, and the clause covers fuel and asphalt only" is far more useful in a later review than an unexplained adjustment in a spreadsheet cell.

Third check: compare risk and contingency

The third check concerns risk. An engineer's estimate is more than unit prices multiplied by quantities. It also reflects the agency's judgment about uncertainty in the project, and that judgment can differ widely from one estimate to another.

The FHWA guidance notes that the AASHTO Practical Guide provides detailed information on how risk and contingency are established for projects of varying complexity in Chapter 5, Risk Based Cost Estimates. That chapter is worth reading if your bid differs from the estimate by a meaningful amount, especially on a project with complex conditions.

Start by listing the project's risk factors in plain terms. Common examples on highway work include unusual subsurface conditions, utility conflicts, staged construction that limits how crews can move, tight right-of-way, weather-sensitive work windows, and work close to live traffic. Then ask whether the estimate and your bid treat each factor the same way.

Some ways to make this check concrete include the following.

• List the risk items in your bid. For each one, note whether you carried it as a separate line, as a percentage markup, or as a contingency built into another item. The method determines how visible the risk is during review.
• Do the same for the estimate, to the extent its documentation shows it. Estimate files may not record every assumption, so ask the agency before you guess what it intended.
• Separate risk you chose to carry from risk the contract already allocates. A bidder who prices a risk that the contract handles elsewhere may overstate cost. A bidder who leaves out a risk that the contract places on the contractor may understate it. Both show up as gaps, but they call for very different responses.
• Check whether a price adjustment clause covers any of the risk. If it does, part of your contingency may be unnecessary, which ties this check back to the second one.
• Treat schedule risk separately from cost risk. A longer or tighter schedule can change labor, equipment, and overhead even when the physical work is the same.

When you write the risk summary, separate known risks from unknown ones. Known risks usually have identifiable triggers and can often be priced with a specific allowance. Unknown risks are harder to price directly, so bidders tend to carry them as contingency. Keeping the two apart makes it clearer what the contingency is buying.

A useful habit is to describe each risk in one sentence, then describe how it was priced in one more sentence. If you cannot write either sentence clearly, you probably have not understood the risk well enough to judge the difference. That is a signal to go back to the plans, the special provisions, and the site information the agency provided.

A large contingency can also be covering missing information. If a bid carries a big allowance because site records were thin, the most useful response may be a question to the agency about the available records, not a debate about the percentage. Likewise, if the estimate assumed conditions that the plans do not describe, the difference may point to a documentation gap rather than a pricing gap.

Risk comparisons are also where professional judgment matters most. Two reasonable estimators can look at the same project and reach different contingency levels. The goal of this check is not to force agreement. It is to understand where the disagreement lies and whether the difference is defensible.

Putting the checks together

Once you have worked through the three checks, write a short summary that someone else can follow without a long conversation. A useful structure answers four questions.

• Did the estimate and the bid describe the same work? Answer yes, no, or partly, and say where the differences are.
• How did each one treat price changes over time? Note the price date, the relevant clause, and the escalation assumptions on each side.
• How did each one treat risk and contingency? Name the main risk items and the method used to price each of them.
• What remains unexplained? These items are the questions to take to the agency or back to your own team, and they are the ones most worth raising in a formal request for clarification.

Keep a log of which assumptions you verified and which you did not. Unverified assumptions are the ones most likely to change when the project is revisited.

A gap that is explained by scope, timing, and risk is usually not a problem in itself. It is the normal result of two parties pricing the same project with different assumptions. A gap that remains after those explanations are applied deserves attention, and a clear summary will make that conversation far more productive.

Anyone preparing a bid should be ready to say what they assumed and why. Anyone who needs the agency's assumptions should ask in writing if the answer matters to the decision in front of them. A written question is not an accusation. It creates a record that both sides can rely on later, and it keeps the discussion on the facts.

Illustrative example: explain a price gap

First confirm that both cover the same quantity and work. Then compare price dates and adjustment coverage. Finally, check risk allowances. Record any explanation beside the item; if the gap remains unexplained, write a specific question for review rather than changing the bid just to match.

Common mistakes to avoid

Several mistakes come up again and again when people compare an engineer's estimate with a bid. Watching for them can save a lot of time.

• Comparing totals only. Totals hide offsetting differences. One line may sit far above the estimate while another sits far below, and the net gap looks small. Compare line by line first, then compare totals.
• Treating a single unit price as evidence. One unit price can reflect a specific method or supplier arrangement, so check the surrounding items before drawing a conclusion.
• Assuming the estimate is always right, or always wrong. An engineer's estimate is a professional judgment built on stated assumptions. Treat it as a well-informed reference point, not as a verdict on your bid.
• Letting small differences distract you from large ones. Sort the differences by size and effect before deciding where to spend your time. A dozen small variances rarely explain a large gap, while one large variance often does.
• Treating the comparison as the end of the analysis. The comparison tells you where to look, not what the answer is.

Where to go next

After the reference material, turn to your state's own bid review procedures and to the contract documents for your specific project. Your agency's procedures and the signed contract govern your project, and they may differ from the general guidance in ways that matter. The checks in this post are a way to organize your questions, not a substitute for the answers that the project documents provide.

Today, choose the largest unexplained bid-item gap and write down its scope match, price dates, adjustment coverage, and risk allowances. Turn any missing explanation into a written question for your team or the agency.

Questions about the estimate

What should I check first?

Start by matching the work, quantities, and units in the estimate and bid.

What should I record after the comparison?

Record the assumptions you checked, the differences they explain, and the questions that remain.