Estimating is a crucial aspect of the construction process, serving as the foundation for project budgets and timelines. As estimators work diligently to produce accurate estimates, they inevitably encounter challenges and make mistakes along the way. These errors are part of the learning curve, allowing estimators to refine their skills and improve their craft. In this blog post, we will explore some common mistakes that every estimator has likely made at least once and the valuable lessons they can impart.

Underestimating Material Quantities

One of the most common mistakes for estimators is underestimating material quantities or scope. In a competitive bid, estimators may fail to perform an accurate quantity takeoff, thus miscalculating the amount of materials needed, leading to budget overruns and potential delays during construction. To avoid this error, estimators must be thorough in their evaluation of the plan set and ensure that they've captured the entire scope of work.

Overlooking Labor Costs

Estimators may occasionally overlook labor costs, focusing too heavily on material expenses. Skilled labor is a significant contributor to project costs, and omitting labor estimates can lead to unrealistic budget projections. To address this, estimators must diligently account for labor hours and rates, considering the complexity of tasks, unique site factors, and potential overtime requirements.

Ignoring Site Conditions

Estimators who fail to account for site-specific conditions can encounter challenges during construction. Site conditions, such as soil type, topography, and accessibility, can significantly impact project costs. Estimators must thoroughly assess the site and factor in any necessary adjustments to their estimates.

Relying Solely on Historical Data

While historical data is a valuable resource, relying solely on past project data can lead to inaccuracies. Each construction project is unique, and estimators must consider the project's specific requirements, design, and current market conditions. Combining historical data with current information ensures more accurate estimates.

Overlooking Scope Changes

Change orders are a common occurrence in construction projects. Change orders can take considerable time to approve and hold progress up on a job. Estimators who fail to account for potential scope changes and schedule impacts can find themselves facing cost overruns and project delays. Anticipating scope changes and incorporating contingencies in estimates can help mitigate these risks.

Neglecting to Verify Quotes

Estimators sometimes rely on subcontractor and supplier quotes without thoroughly verifying their accuracy. Mistakes or miscommunications in quotes can lead to discrepancies in estimates. Estimators should double-check and compare all quotes to ensure that all costs are correctly accounted for in the estimate. Modern cloud-based software, like BuildBoss's Bid Management Pro, makes quick work of communicating with subs and suppliers. It also leaves a nice digital trail that you can go back and review in case you ever have any questions regarding your communications together.

Failing to Review and Refine Estimates

In the rush to meet deadlines on bid day, estimators may neglect to review and refine their estimates. Regularly reviewing estimates, seeking feedback from colleagues, and conducting post-project evaluations can help identify areas for improvement and enhance estimating accuracy over time.


Mistakes are an inevitable part of the estimating process, and every estimator has encountered them in their career. These errors provide valuable learning opportunities, allowing estimators to refine their skills, improve their processes, and deliver more accurate estimates. By addressing common mistakes, such as underestimating material quantities, overlooking labor costs, ignoring site conditions, relying solely on historical data, neglecting scope changes, failing to verify subcontractor and supplier quotes, and skipping estimate reviews, estimators can enhance their proficiency and contribute to the success of construction projects and their company.

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