Estimate

An estimate is a quantified prediction of the effort, duration, or cost required to complete a defined scope of work, carrying explicit assumptions and a known confidence level that together determine its reliability. On fixed-fee engagements, the estimate determines the price; estimation error translates directly into margin loss.

Types of estimates

Rough order of magnitude (ROM): an early-stage estimate produced before full scope definition, used for budgeting conversations. Typical range: minus 25% to plus 75%.

Budgetary estimate: produced after initial scoping with a clearer work breakdown structure. Used for proposal pricing. Typical range: minus 10% to plus 25%.

Definitive estimate: built from a detailed WBS with validated assumptions and historical actuals. Used for fixed-fee statements of work. Typical range: within plus or minus 10%.

The type of estimate must be stated alongside the number. A ROM that gets anchored as a definitive commitment is a margin problem before the engagement starts.

What a strong estimate includes

• A complete WBS with tasks at the work-package level
• Effort in hours by role or seniority level, not just total hours
• A stated confidence level and the assumptions it depends on
• An explicit risk buffer or contingency, separated from the base estimate
• A reference to historical actuals from similar engagements

Estimate vs. budget vs. price

	Estimate	Budget	Price
What it is	Projected cost to deliver	Approved spend ceiling	What the client pays
Who sets it	Delivery team	Finance or leadership	Account or BD team
Built from	WBS and actuals	Estimate plus margin	Estimate plus margin plus positioning

Tracking estimate accuracy over time

Comparing estimates to actuals at engagement close-out produces the calibration data that improves future estimates. Firms that track estimate-to-actual variance by engagement type and practice line consistently produce more accurate estimates than those that treat each engagement as a fresh start. An engagement template that embeds historical actuals in its budget model is the most direct way to transfer that calibration into future work.

Common causes of estimate overruns

Underestimating integration complexity, omitting project management and governance hours, failing to account for client review cycles, and anchoring on a budget number rather than on the actual scope are the most frequent sources of cost overrun on fixed-fee work. Estimating bias compounds this when teams adjust estimates to fit a target price rather than a genuine bottom-up calculation.