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Base estimate

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The estimated cost of the defined scope at current prices, before contingency, escalation and reserves are added — the "what we can see, at today's money" figure.

The base estimate is the deterministic core of a total estimate: measured quantities priced at base-date rates, plus indirects, with the provisions for uncertainty stripped out and shown separately. Structuring estimates this way is what makes them auditable. Reviewers can interrogate the base against the drawings, the contingency against the risk register, and the escalation against the expenditure schedule — three separate conversations instead of one argument about a single number.

It also makes estimates comparable over time. When the estimate is restated at the next design stage, movement in the base reveals scope and quantity growth, while movement in contingency reveals changing risk — provided the boundary was kept clean.

Keeping it clean is the entire discipline. Allowances hidden in quantities and padding tucked into rates are contingency smuggled into the base, and once there, they can never be separated out again. An estimate whose base cannot be reconciled to the documentation is not conservative; it is simply unexplainable.

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