Estimating Bias / Padding

Estimating bias is a systematic tendency to produce project estimates that consistently deviate from actual effort, either through optimism bias (underestimation) or strategic padding (overestimation), distorting proposal pricing and delivery outcomes.

Optimism bias

Optimism bias is the most common form. Estimators focus on the best-case scenario, plan as if no problems will occur, and anchor on what they want the project to cost rather than what similar projects actually cost. The planning fallacy, a documented cognitive pattern in which people underestimate the time and cost of future work even when they know their past projects ran over, is the underlying mechanism.

Signs of optimism bias:

• Engagement-level actuals are consistently 110 to 140% of estimates
• Integration and testing tasks are repeatedly underestimated
• Senior delivery leads add hours during execution that were not in the proposal
• The firm’s standard project type takes longer on every engagement

The cost appears as margin erosion on fixed-fee work or as overruns that strain client relationships on time-and-materials engagements.

Strategic padding

Padding is the attempt to protect margin by inflating individual task estimates. It is often well-intentioned but creates its own problems.

Signs of strategic padding:

• Win rate on fixed-fee bids is low despite a strong delivery track record
• Clients routinely negotiate prices down and the firm accepts, implying the original price had room
• Estimators cannot explain specific line items when challenged

Padding also cascades: when individual tasks are padded, teams expand to fill the available time (Parkinson’s Law), so actual delivery does not get faster even though the margin appears protected on paper.

Calibrated estimation

Calibrated estimation replaces bias with data. A contingency reserve is not the same as padding: a contingency reserve is an explicit, visible buffer for identified risks, stated as a separate line in the estimate. Padding is hidden inflation spread across individual task estimates.

Steps toward calibration:

1. Track variance: record estimate vs. actual for every engagement by phase, role, and project type
2. Use reference classes: anchor new bottom-up estimates to the distribution of actual costs from comparable past work, not to the current plan
3. Separate contingency explicitly: add a visible risk buffer as a separate line, sized to identified risks, not hidden in task inflation
4. Review by the delivery lead: the person who will execute the work reviews the estimate before submission

Calibrated estimate = Bottom-up task sum + Explicit contingency
Contingency = Identified risk hours x Probability of occurrence

Firms that track estimate variance systematically against actuals over time gain the historical cost data needed to reduce systematic error in both directions.