How to Do a Construction Cost Estimate: 10 Steps for Contractors

To prepare a construction cost estimate, review the bid documents, measure every quantity of work, price it with labor, material, equipment and subcontract costs, add general conditions and markups, and check the total before it goes out. The steps below are the sequence used by estimating departments on US commercial and residential projects.

Key takeaways

• Read the whole solicitation first: instructions to bidders, bid form, specifications and every addendum.
• Measure before you price, and keep quantities traceable to marked-up plans.
• Use subcontractor quotes for scopes you do not self-perform, and level them to a common scope.
• Check the final number against a ratio such as cost per square foot before submitting.

Step 1: Review the bid documents

Read the invitation, instructions to bidders, bid form, general and supplementary conditions, specifications and drawings. List the due date, required forms, bid security, alternates, unit prices, allowances, liquidated damages and any prevailing wage or Davis-Bacon requirements. Use the guide to reading a construction solicitation if the package is large.

Step 2: Attend the pre-bid meeting and visit the site

Site conditions drive cost: access, staging area, existing utilities, overhead lines, soil, traffic control and working hours. Take photos and notes. The pre-bid conference is where the owner explains the schedule and bid procedure and answers questions.

Step 3: Send RFIs and log addenda

Submit written requests for information before the question deadline. Log every addendum and update the drawing and specification set so the estimate reflects the latest documents. Missing an addendum is one of the most common reasons for a wrong or non-responsive bid.

Step 4: Break the project into trades

Organize the work by CSI MasterFormat division or by your own cost codes. Decide which trades you will self-perform and which you will buy from subcontractors, and send scope sheets to the latter.

Step 5: Take off quantities

Measure areas, lengths, volumes and counts from the drawings using digital takeoff software or paper plans. Add waste factors where appropriate, and keep a marked-up set so a second person can check the work. See quantity takeoff explained and material takeoff vs quantity takeoff.

Step 6: Price labor, material and equipment

Labor cost is hours times the wage rate plus burden (taxes, insurance and fringe benefits). Material cost comes from supplier quotes or current price data, with delivery and tax. Equipment cost comes from rental quotes or owned-equipment rates. Use productivity rates that match the site, the crew and the work method.

Step 7: Bring in subcontractor and supplier quotes

Compare quotes on the same basis. Bid leveling adjusts each proposal for inclusions and exclusions so the lowest number is also the most complete.

Step 8: Add general conditions and project-wide costs

Include supervision, temporary facilities, utilities, safety, cleanup, permits, insurance, testing and the cost of the schedule duration. These costs scale with time, so a longer schedule raises them.

Step 9: Apply markups, bonds and contingency

Add overhead and profit, sales tax where it applies, bond premiums and a contingency matched to the risk in the documents. Price alternates, allowances and unit prices separately as the bid form requires.

Step 10: Review, compare and document

Have a second person check quantities and math. Compare the result to cost per square foot, cost per unit of use and the cost split between trades. Write down assumptions, exclusions and clarifications. Then complete the bid form and submit before the deadline.

A bid-week timeline

Estimators work backward from the bid date. A realistic schedule for a mid-size commercial bid might look like this, adjusted for project size: on day one, download documents, build the bid-day checklist and send invitations to subcontractors; on days two and three, read the specifications, log questions and start the takeoff; midweek, send RFIs and scope sheets and begin collecting quotes; in the last two days, level proposals, finish pricing, add general conditions and markups and run the final review. Leave the last hours for the bid form, bonds and delivery rather than for pricing.

Checklist before you submit

• Every addendum is acknowledged on the bid form and reflected in the estimate.
• All alternates, unit prices and allowances are priced as the form requires.
• Required forms, bid security, licenses and insurance certificates are attached.
• The wage requirement (prevailing wage or Davis-Bacon) is reflected in labor.
• Subcontractor quotes are leveled and any gaps are carried or clarified.
• The total is compared with cost per square foot and the trade split.
• The bid form is signed by an authorized person and delivered the way the instructions require.

Where the cost estimate goes wrong

Estimating errors fall into a few groups. Quantity errors come from reading the wrong scale, missing a sheet or double-counting. Pricing errors come from outdated unit costs, wrong productivity or quotes that exclude work the estimate assumed. Scope errors come from gaps between trades, where each subcontractor assumes someone else carries an item. Process errors come from missing addenda or a late start. A written checklist and a second reviewer prevent most of them.

Residential versus commercial estimating

The method is the same, but the details differ. Residential estimates are often organized by phase (site, foundation, framing, mechanical, finishes) and rely on allowances for owner selections such as flooring and fixtures. Commercial estimates are usually organized by CSI division, rely on formal specifications and more subcontractor quotes, and must respond to bid forms, alternates and insurance and bond requirements. Public projects add wage rules, prequalification and strict responsiveness requirements.

Tools that help

• Digital takeoff software for measuring plans, and Excel or an estimating database for pricing.
• A cost database or past job-cost history for unit costs and productivity.
• A bid-day checklist and a standard scope sheet for each trade.
• A quote-comparison sheet for leveling subcontractor proposals.

When to get help

If several bids are due in the same week, outside support for takeoff and pricing keeps the schedule realistic. Bid Sharp prepares construction estimates and pre-bid support in Excel and PDF; upload your plans with the bid date for a firm price and turnaround before work starts.