Estimate type: concept to design development
Rough order of magnitude estimate and conceptual budgets
A rough order of magnitude estimate tells an owner whether a project is in the right range before design is finished. Bidmere builds ROM and conceptual budgets from early drawings, with every assumption written down.
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Typical ranges from AACE International Recommended Practice 56R-08 for building and general construction, at an 80% confidence interval after contingency.
Quick answer
A rough order of magnitude estimate (ROM estimate) from Bidmere is an early construction budget built from concept, schematic or design development drawings. General contractors and design-build teams get cost by system or division, the pricing basis for each line, an assumptions register and the AACE estimate class. Multi-trade budgets are from $1,150, with a fixed quote first.
What is a rough order of magnitude estimate?
A rough order of magnitude estimate is the first cost number on a project, prepared when design is only a concept or a program. It answers one question: is this project roughly affordable, and in what range?
In AACE International’s classification for building and general construction (Recommended Practice 56R-08), a ROM usually falls in Class 5 or Class 4. Class 5 supports early concept screening. Class 4 supports schematic design and concept studies.
Other names you will hear for the same early number:
- ROM estimate or order of magnitude estimate
- Conceptual estimate
- Budget estimate or preliminary estimate
- Feasibility estimate
The names overlap. What matters is how mature the design is. AACE ties each class to the share of project definition complete, so readers know what the number can support.
How accurate is a ROM estimate? AACE estimate classes explained
A ROM estimate is a range, not a price. AACE RP 56R-08 gives typical accuracy ranges by class for building and general construction, at an 80% confidence interval after contingency.
| Class | Project definition | Typical use | Typical method | Accuracy low | Accuracy high |
|---|---|---|---|---|---|
| 5 | 0% to 2% | Concept screening | Area-based factoring, parametric models, analogy | -20% to -30% | +30% to +50% |
| 4 | 1% to 15% | Schematic design, concept study | Parametric and assembly models | -10% to -20% | +20% to +30% |
| 3 | 10% to 40% | Design development, budget authorization | Semi-detailed unit costs, assembly line items | -5% to -15% | +10% to +20% |
| 2 | 30% to 75% | Control or bid at semi-detailed level | Detailed unit costs, forced detailed takeoff | -5% to -10% | +5% to +15% |
| 1 | 65% to 100% | Check estimate, bid, change order | Detailed unit costs, detailed takeoff | -3% to -5% | +3% to +10% |
AACE notes these are reference ranges. A specific project’s range should come from risk analysis. A class label alone is not a promised accuracy.
Preliminary vs ROM vs conceptual estimate
The three names are not standard terms, and firms use them differently. In common use they mark how far design has gone, which sets the method and the likely range.
| Estimate | Typical design stage | Usual method | Closest AACE class |
|---|---|---|---|
| ROM (rough order of magnitude) | Program or concept, few or no drawings | Cost per square foot or per unit from historical data | Class 5 or Class 4 |
| Conceptual estimate | Concept or early schematic drawings | Square foot, parametric or early systems pricing | Class 5 or Class 4 |
| Preliminary estimate | Schematic design to design development | Assemblies by building system, with some measured quantities | Class 4 or Class 3 |
| Bid estimate, for contrast | Construction documents | Detailed takeoff and unit costs | Class 2 or Class 1 |
Because one firm’s preliminary estimate is another’s conceptual budget, ask which drawings a number is based on and which class it claims, then read its range in the table above. When the documents are complete enough to bid, see bid estimates.
How is a conceptual estimate built?
A conceptual estimate prices what the design shows and states what it assumes for the rest. The method follows the documents available.
- Square foot or unit method. Cost per gross square foot, per unit, per bed or per parking stall, from historical or published data, adjusted for location and time.
- Parametric method. Costs driven by key parameters such as floor area, stories, perimeter, wall-to-floor ratio and site area.
- Assembly or systems method. Cost by building system: foundations, structure, enclosure, roofing, interiors, MEP, sitework. This is the usual method once schematic plans exist.
- Allowances. Fixed amounts for scope not yet designed, stated as allowances.
- Escalation and contingency. Added as factors you set for the schedule and the risk.
On early jobs, the assumptions register matters as much as the number. It tells the owner what is in the budget and what would change it.
Construction budget template: what a ROM budget should show
A useful construction budget template keeps the number and its basis together. Each line should show:
- Building system or MasterFormat division
- Key quantity and unit, such as gross floor area in SF, roof area in SF or site area in acres
- Pricing basis: square foot, parametric, assembly or unit cost
- Unit cost and extended cost
- Data source and date, so the number can be escalated later
- Assumption for design not yet shown
Below the direct costs, show general conditions, contractor fee, design contingency, escalation and owner items separately. Mixing them into unit costs hides the risk the owner is carrying.
The free construction budget template from Bidmere follows this layout in Excel. Pair it with the construction estimate template once drawings reach design development.
Have plans for this scope? Send them over. Fixed quote within 2 business hours. Plan review is free, and you pay only after you accept.
Get a fixed quoteWhat do early budgets usually miss?
Early budgets go wrong because scope is missing, not because unit costs are off. Check for these before the number goes to an owner:
- Structural system not selected, so foundations and frame are guessed
- Mechanical and electrical described only in narrative
- Site and utility work outside the building footprint
- Off-site utility extensions and impact fees
- Finish quality level not stated
- Geotechnical conditions unknown, such as rock or poor soils
- Code-driven items: fire sprinklers, fire alarm, accessibility upgrades
- Phasing, occupied-building work or night shifts
- Escalation to the midpoint of construction
- Design and owner contingency kept separate from construction contingency
ROM and budget estimating service: what you send and what you get
Send the drawings you have and the cost data you trust. We return a budget organized by system, with the basis and assumptions written down. Your team sets contingency and decides how the number is used.
You send
- Concept, schematic or design development plans
- Program or outline specification, if available
- Site information and any geotechnical findings
- Historical costs or rates you approve
- Target budget or design options to compare
You get
- Budget summary by system or division, with the pricing basis on each line
- Assumptions register for what the design does not show yet
- Option comparison for design choices you ask us to test
- Classification note stating the design stage and AACE class
- Delivery as an Excel estimate with live formulas, color-coded marked-up PDF plans, and a written list of assumptions, exclusions and open questions
Not included: design or engineering decisions, market forecasts beyond the factors you approve, firm pricing commitments, and site visits. A budget is not a bid.
Sample takeoff
What a takeoff looks like
| System | Quantity | Unit | Pricing basis |
|---|---|---|---|
| Foundations and slab on grade | 12,000 | SF | Assembly, spread footings assumed |
| Structure: steel frame and roof deck | 12,000 | SF | Parametric by bay size |
| Exterior enclosure | 7,200 | SF wall | Assembly, 40% glazing assumed |
| Roofing | 12,600 | SF | Unit cost, TPO assumed |
| Interior construction and finishes | 12,000 | SF | Square foot, mid-grade finishes |
| Plumbing, HVAC, fire protection | 12,000 | SF | Square foot, narrative only |
| Electrical and low voltage | 12,000 | SF | Square foot, narrative only |
| Sitework and utilities | 1.8 | AC | Allowance, no civil drawings |
Fictional example: Class 4 ROM summary layout for an invented 12,000 SF one-story office. Quantities and bases only; unit costs come from data you approve.
Before you send plans
Common questions about handing off the work
Can a remote team price a project with so little design?
Yes, as long as the gaps are written down. Every line names its basis and assumption, so your team can adjust what it knows better.
Whose cost data is used?
Yours, or sources you approve. You set escalation, contingency and fee.
Will the owner treat this as a price?
The classification note states the AACE class and intended use, so the number is read as a budget range, not a bid.
Monthly estimating plans
Running preconstruction on several jobs? Use a monthly plan.
Design-build and preconstruction teams often need a budget at every design milestone. Monthly estimating plans cover recurring work: $1,395 per month for up to 6 bids, $2,595 per month for up to 12 bids or $4,795 per month for up to 25 bids, using your cost data every time.
Questions
Frequently asked questions
What is a ROM estimate in construction?
A ROM estimate, or rough order of magnitude estimate, is an early cost range built before design is far along. It is used to test feasibility and set a first budget. Under AACE RP 56R-08 it usually sits in Class 5 or Class 4, with typical ranges as wide as -30% to +50% for Class 5.
What is the difference between a ROM estimate and a budget estimate?
The terms overlap. A ROM is usually the earliest number, from a program or concept. A budget estimate is often built from schematic or design development drawings and used to authorize funding, which AACE places around Class 3. The design stage, not the label, sets what the number can support.
How accurate is a conceptual estimate?
It depends on design maturity, project risk and the quality of cost data. AACE RP 56R-08 gives reference ranges, such as -20% to -30% low and +30% to +50% high for Class 5. AACE says a specific project’s range should come from risk analysis. A class label is not a promised accuracy.
How much does a ROM estimate cost?
Multi-trade budgets from Bidmere are from $1,150, and a single-system budget is priced from $195. You get a fixed quote within 2 business hours after we review your drawings, and you pay only after you accept the fixed price and delivery date.
What do I need to send for a budget estimate?
The current design documents, any program or outline specification, site information, and the cost data or rates you want used. Add your target budget or design options if you want them compared. You approve the assumptions, contingency and escalation before the number is used.
Is there a free construction budget template?
Yes. Bidmere’s free construction budget template is an Excel sheet organized by building system, with columns for quantity, unit, pricing basis, unit cost, data source and assumption. Contingency, escalation and fee sit below the direct costs. It opens in Google Sheets.
Can you update the budget as design progresses?
Yes. Each design milestone is quoted as its own update. We carry the assumptions register forward, mark what the new drawings resolved and show what moved. That gives the owner a clear trail from the first ROM to the bid-day number.
Do you use cost per square foot data?
When the design is only a program, yes, from sources you approve, adjusted for location and date. Published per square foot ranges are a starting point, not an answer. As soon as plans exist, we move to assemblies and measured quantities.
Get a fixed quote
Share the project basics. You get a fixed price and delivery date within 2 business hours. Plan review is free, and you pay only after you accept.