| Project definition | 65% to 100% of full definition |
|---|---|
| Typical end usage | Check estimates, bid validation, change orders, claims and disputes |
| Estimating method (general, RP 18R-97) | Detailed unit costs with detailed take-off |
| Estimating method (road and rail, RP 98R-18) | Unit-rate line items on actual design quantities, usually for critical parts of the project |
| Expected accuracy (80% confidence) | Low: −3% to −10% High: +3% to +15% |
| Other names | Definitive, check estimate, fair price, firm price, bottom-up, change order estimate |
| Typical stage | Execution; Queensland PCEM: Implementation (pre-award validation) |
AACE Estimate Classification: Check Estimate or Bid/Tender
AACE Class 1 Estimate
The most detailed estimate in the system. A Class 1 estimate is usually prepared for critical parts of a project to check a bid, price a change or resolve a claim.
Updated 2 October 2026
At a Glance
Class 1 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 1 Estimate Is
A Class 1 estimate is prepared when 65% to 100% of the project is defined, with some owners calling for a 90% design review. Virtually all design documentation exists, along with complete execution and commissioning plans.
The expected accuracy is -3% to -10% on the low side and +3% to +15% on the high side. Even at full design, the range is not zero: productivity, market conditions and site conditions still vary.
Because the effort is high, Class 1 estimates are rarely prepared for an entire project. They are targeted at the packages where precision matters most: a large subcontract, a disputed variation, or a tender that looks too low.
What needs to be defined
Typical status of key deliverables for a road or rail project at Class 1. The class follows the weakest deliverable that materially affects cost, not the average.
- All or nearly all design deliverables complete (issued for construction)
- Complete specifications and tender documentation
- Execution, staging and commissioning plans complete
- Long-lead items in fabrication or on order
How it is prepared
Every item is a unit-rate line priced on actual design quantities, with rates built up from labour, plant, materials and subcontract prices. The estimator works at the level a contractor would plan the work.
This is the class used to check whether a tender price is fair, to evaluate variations, and to support claims and dispute resolution, where the estimate may be tested line by line.
Worked Example
What the Class 1 Range Means in Dollars
Illustrative figures for an independent check estimate for a bridge package before contract award: an estimate of $12M including contingency.
| Project risk profile | Accuracy range | 80% confidence range of final cost |
|---|---|---|
| Well understood, low risk (tight end of the band) | −3% / +3% | $11.64M to $12.36M |
| Complex or high risk (wide end of the band) | −10% / +15% | $10.8M to $13.8M |
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 1 Mistakes
- Preparing a 'definitive' estimate for the whole project when only critical packages justify the effort
- Assuming design is complete when some packages are still at Class 2 maturity
- Comparing a Class 1 check estimate with a tender on a different scope or risk allocation
- Treating a Class 1 range as guaranteed: unusual site or market conditions can still push outcomes outside it
In Queensland, a Class 1 estimate broadly corresponds to the PCEM Implementation (pre-award validation) 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 1 estimate?
A Class 1 estimate is the most defined class in the AACE system, prepared with 65% to 100% of project definition using detailed unit costs and detailed take-off. Its expected accuracy is -3% to -10% on the low side and +3% to +15% on the high side at 80% confidence.
Is a Class 1 estimate the same as a definitive estimate?
Definitive, check, fair price and firm price estimates are all common names for Class 1. The class ties the name to a defined level of project maturity.
When is a Class 1 estimate used?
Mainly for check estimates before contract award, for bid validation, and for pricing changes, claims and disputes. It is usually prepared for critical packages rather than the whole project.
Need AACE-Classified Cost Estimates?
Cenex delivers rigorously classified cost estimates aligned with AACE Recommended Practices for Australian infrastructure projects.