| Project definition | 30% to 75% of full definition |
|---|---|
| Typical end usage | Detailed control baseline, pre-tender estimate, contractor's tender |
| Estimating method (general, RP 18R-97) | Detailed unit costs with forced detailed take-off |
| Estimating method (road and rail, RP 98R-18) | Detailed unit-rate line items from measured quantities; assumed (forced) detail where design is incomplete |
| Expected accuracy (80% confidence) | Low: −5% to −15% High: +5% to +20% |
| Other names | Detailed control, pre-tender, tender, engineering, master control, execution phase |
| Typical stage | After FEL (detailed design); Queensland PCEM: Development (pre-tender, S2D) |
AACE Estimate Classification: Control or Bid/Tender
AACE Class 2 Estimate
The estimate that sets the control baseline. A Class 2 estimate is detailed enough for contractors to bid from and for owners to test those bids.
Updated 2 October 2026
At a Glance
Class 2 Estimate Characteristics
The five attributes AACE uses to describe each class. Project definition maturity is the one that decides the class; the others follow from it.
Overview
What a Class 2 Estimate Is
A Class 2 estimate is prepared when 30% to 75% of the project is defined, often around a 60% design review. Design is well advanced, bulk materials can be quoted, most land and approvals are in hand, and contracts may already be in place for early works.
The expected accuracy is -5% to -15% on the low side and +5% to +20% on the high side. At this level the estimate is used to control cost: actual costs are monitored against it and changes are measured from it.
For contractors, the tender estimate is usually Class 2. For owners, the pre-tender estimate is the benchmark against which tenders are evaluated, so its quality directly affects whether a low tender is recognised as too low.
What needs to be defined
Typical status of key deliverables for a road or rail project at Class 2. The class follows the weakest deliverable that materially affects cost, not the average.
- Detailed design well advanced across road, rail, structures and systems
- Bulk materials quoted and major equipment specified
- Most land, permits and licences obtained
- Supply and construction contracts issued or ready to issue
How it is prepared
Class 2 estimates are fully bottom-up and can run to thousands of line items. Quantities come from detailed take-off; where parts of the design are still incomplete, the estimator assumes a level of detail (a 'forced' take-off) rather than falling back on factors.
Rates are built up from first principles or current market prices, and the estimate is structured to match how the work will be packaged, tendered and controlled.
Worked Example
What the Class 2 Range Means in Dollars
Illustrative figures for a pre-tender estimate for a road reconstruction package at around 60% design: an estimate of $18M including contingency.
| Project risk profile | Accuracy range | 80% confidence range of final cost |
|---|---|---|
| Well understood, low risk (tight end of the band) | −5% / +5% | $17.1M to $18.9M |
| Complex or high risk (wide end of the band) | −15% / +20% | $15.3M to $21.6M |
Try it with your own estimate
The accuracy range calculator applies the published bands for every class to your figure, and shows where your project might sit within them.
Open the calculatorAACE stresses that these bands are typical outcomes, not targets. The range for a particular estimate should come from a quantitative risk analysis. See P50 and P90 explained.
Avoid These
Common Class 2 Mistakes
- Rolling a Class 3 estimate forward with escalation instead of re-estimating from the detailed design
- Ignoring the contractor's view of risk, so the pre-tender estimate sits well below every tender received
- Losing the link between the estimate structure and the contract packaging, which makes cost control harder
- Treating the narrower range as permission to remove contingency that still covers real risks
In Queensland, a Class 2 estimate broadly corresponds to the PCEM Development (pre-tender, S2D) phase. The mapping is approximate; see AACE vs PCEM for how the two frameworks line up.
FAQ
Frequently Asked Questions
What is an AACE Class 2 estimate?
A Class 2 estimate is prepared with 30% to 75% of project definition to form a detailed control baseline or a tender estimate. It uses detailed unit costs with forced detailed take-off and has an expected accuracy of -5% to -15% on the low side and +5% to +20% on the high side at 80% confidence.
Is a pre-tender estimate a Class 2 estimate?
Usually. Owner pre-tender estimates and contractor tender estimates are typically prepared from detailed design and fall within Class 2, although parts of a project may be estimated at Class 1.
What is a forced detailed take-off?
Where some design is still incomplete, the estimator assumes a realistic level of detail and measures it, instead of using a factor. This keeps the estimate in line-item form so it can be updated as design completes.
Need AACE-Classified Cost Estimates?
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