Data Source and Methodology
Authoritative data source: RSMeans City Cost Index (Gordian), 2024 Edition. Access: https://www.rsmeans.com/. This calculator applies a parametric approach: baseline unit costs by building type and quality, adjusted by a location factor and project-specific percentages.
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.
The Formula Explained
Let \(A\) be area, \(U\) the baseline unit cost, \(L\) the location factor, \(C\) the complexity factor, \(s\) soft costs (as a decimal), \(g\) contingency, \(p\) overhead & profit, \(r\) annual escalation, and \(m\) months to midpoint.
Base cost: \( \mathrm{Base} = A \times U \times L \times C \)
Soft costs: \( \mathrm{Soft} = \mathrm{Base} \times s \)
Contingency: \( \mathrm{Cont} = (\mathrm{Base}+\mathrm{Soft}) \times g \)
Overhead & Profit: \( \mathrm{OP} = (\mathrm{Base}+\mathrm{Soft}+\mathrm{Cont}) \times p \)
Subtotal: \( \mathrm{Sub} = \mathrm{Base}+\mathrm{Soft}+\mathrm{Cont}+\mathrm{OP} \)
Escalation factor: \( E = (1 + r)^{\,m/12} \)
Total: \( \mathrm{Total} = \mathrm{Sub} \times E \)
Unit cost: \( \mathrm{Unit} = \frac{\mathrm{Total}}{A} \)
Glossary of Variables
- Floor area (A): total gross area to be constructed in ft² or m².
- Unit cost (U): baseline construction cost per area for type and quality.
- Location factor (L): city cost multiplier; 1.00 = national average.
- Complexity factor (C): adjustment for unusual structure/site/systems.
- Soft costs (s): design, permits, insurance, CM; entered as a percent.
- Contingency (g): risk allowance; entered as a percent.
- Overhead & profit (p): contractor markup; entered as a percent.
- Annual escalation (r): expected annual price growth (decimal).
- Months to midpoint (m): months until mid-point of construction.
- Total project cost: sum after escalation to midpoint.
- Unit cost: total project cost divided by area, in $/ft² or $/m².
Worked Example
How it works: a step-by-step example
Assume a 25,000 ft² standard office in Denver, 2 floors, national unit cost baseline, soft 15%, contingency 10%, O&P 12%, complexity 1.00, annual escalation 4%, midpoint 12 months.
- Baseline unit cost (U) for Standard Office ≈ $240/ft². Location (L) Denver ≈ 1.03. Complexity (C)=1.00.
- Base = A × U × L × C = 25,000 × 240 × 1.03 × 1.00 = $6,180,000.
- Soft = Base × 0.15 = $927,000.
- Cont = (Base + Soft) × 0.10 = ($6,180,000 + $927,000) × 0.10 = $710,700.
- OP = (Base + Soft + Cont) × 0.12 ≈ $963,684.
- Sub = Base + Soft + Cont + OP ≈ $8,781,384.
- Escalation factor E = (1 + 0.04)^(12/12) = 1.04. Total = Sub × E ≈ $9,132,639.
- Unit cost = Total / A ≈ $365.31/ft².
Use your own area, factors, and percentages to reflect scope and market conditions.
Frequently Asked Questions (FAQ)
How accurate is this estimator?
It is a conceptual tool (AACE Class 5–4). Expect a wide range until design is further developed and quotes are obtained.
What is a location factor?
A multiplier that adjusts national average costs to a specific city or region, derived from published indices like RSMeans.
What should i include in soft costs?
Architecture, engineering, permits, plan review, inspections, surveys, utility fees, insurance, testing, and project management.
How do i select contingency?
Early phases often use 10–20%, reducing as risk is retired and design matures.
Does the estimator include taxes?
Sales/VAT is not automatically included. Add it within soft costs or O&P if applicable in your jurisdiction.
Can i switch to metric?
Yes. Toggle Metric to enter area in m²; the calculator converts unit costs accordingly.
Can i override the location factor?
Yes. Enter a custom factor from your latest city cost index; it will override the dropdown.