📊 Data Sources
Where Our Cost Data Comes From
Full transparency on every data source, research reference, and building science standard behind our construction cost calculators.
📚 Source-cited
🔬 Formula-verified
🌍 Multi-market research
🔄 Periodically reviewed
Jump to section
Data Source Overview
Our calculators combine market-specific construction research, deterministic formulas, and engineering or building-science references. The house build calculator also uses country pricing profiles and broad local-market multipliers. We do not treat a simple currency conversion as local construction pricing.
Source quality varies by market. When the available evidence is strong enough, a country can use a verified local residential pricing profile. Where coverage is weaker, the calculator keeps the country on a broader planning index and labels the result accordingly. See our Methodology page for the calculation flow.
4Core source types
2Country pricing modes: verified or fallback
1Separate FX layer for display currency
100%Calculator outputs generated by defined formulas
| Source Category | Used For | Role | Review Approach |
|---|---|---|---|
| Country-specific residential cost research | Verified house-build pricing tiers and market assumptions | Primary local calibration | Updated as better market data becomes available |
| Industry & government construction publications | Cost levels, category shares, labor/material trends, and cross-checks | Primary / supporting benchmark | On new publication or material market change |
| Engineering & building-science references | Board feet, density, insulation, ventilation, and other quantity logic | Formula / technical reference | On source or standard revision |
| Exchange-rate feed | Displaying established estimates in another currency | Display conversion only | Automatically refreshed on a separate schedule |
House Build Cost Calculator — Data Sources
The house build cost calculator combines a detailed project model with country-level residential pricing where verified data is available. Construction pricing and currency conversion are intentionally treated as separate layers.
Country Pricing Profiles
Residential construction calibrationFor verified markets, we store researched residential construction ranges in the country's local profile currency. Profiles are organized by basic, standard, premium, and luxury build tiers and include notes on typical construction methods, what the rates generally include, common exclusions, source period, and confidence level.
Used in: Country-level low / average / high house build calibration
The exact source mix varies by country and may include government construction statistics, industry-body publications, residential builder guides, quantity-surveyor market ranges, financial/property research, and other market-specific references. For example, U.S. calibration uses NAHB construction-cost research as a major reference, while other countries use sources appropriate to their own residential markets.
Used in: Creating and cross-checking verified country pricing bands
Local Market & Project Adjustments
Within-country refinementVerified country profiles can include broad multipliers for rural/lower-cost areas, national-average conditions, major metro markets, high-cost or constrained markets, and remote/island/difficult-access projects. These are planning adjustments, not exact city-level price quotes.
Used in: Local Construction Market selector
Project inputs such as floor area, construction type, finish level, foundation, stories, rooms, roofing, exterior materials, mechanical systems, kitchen level, and add-ons adjust the component estimate before the country calibration is applied.
Used in: Detailed house specification model and category breakdown
Fallback Coverage & Currency
Coverage outside verified profilesCountries without a verified local residential cost profile use a broader planning index rather than pretending to have precise local rates. The interface identifies these estimates so users know to validate them against local bids.
Used in: Countries without verified local house pricing
Exchange-rate data is refreshed separately from construction pricing. For verified country profiles, the local construction estimate is established first; FX is used only when the user chooses a different display currency.
Used in: Currency display and manual currency override
Lumber Calculator — Sources & Formulas
The lumber calculator is formula-based for quantity outputs. Cost per board foot is the only market-variable component.
The board foot formula (Thickness_in × Width_in × Length_ft ÷ 12) is a universally accepted standard unit of measure for dimensional lumber volume, used consistently across the North American and Australasian timber industries. This is an exact formula — not an estimate.
Used in: All board foot quantity outputs
The USDA Wood Handbook is the primary engineering reference for wood species properties including density, specific gravity, and moisture content relationships. Species density factors in our lumber weight calculator are sourced from published specific gravity values in this reference. Both green (unseasoned) and kiln-dried density values are used, as moisture content significantly affects weight.
Used in: Lumber weight calculator — species density factors (lbs per board foot)
Random Lengths and RISI are the primary market references for North American lumber pricing by species and grade. Cost-per-board-foot ranges in the lumber calculator are informed by published price series from these sources. As lumber prices are highly volatile, cost outputs use ranges with a disclaimer to verify current local pricing.
Used in: Lumber cost-per-board-foot range (cost output only — quantity is formula-based)
Attic Conversion Cost — Sources
Cost ranges for the attic conversion cost calculator are derived from published renovation cost research and structural conversion benchmarks.
Attic and loft conversion cost ranges are informed by published residential renovation cost surveys. These provide per-square-foot cost ranges by conversion type (room-in-roof, dormer, hip-to-gable, mansard). Because attic conversion costs are highly market-sensitive, our ranges deliberately capture the full spectrum from competitive-market low to complex-project high.
Used in: Attic conversion cost calculator — base cost range by conversion type
Structural engineer fee ranges for attic conversion projects are informed by published fee guidance from structural and civil engineering professional bodies. These are added as a fixed-range line item when dormer or structural modifications are selected. We flag structural engineering as a required step for all dormer attic conversion projects.
Used in: Structural engineer cost line item in attic conversion results
⚠️ Known Data Limitation — Attic Conversion
Attic conversion costs are among the most regionally variable of any residential project type. Our ranges are deliberately wide to accommodate this variability. We strongly recommend treating attic conversion calculator outputs as initial feasibility screening only, and obtaining 2–3 contractor quotes before making any financial commitment.
Insulation & Ventilation — Standards Referenced
Quantity outputs in the attic insulation calculator and attic ventilation calculator are deterministic — based on established building science standards.
R-value per inch of insulation by material type is published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and insulation manufacturers' technical data. These values are used directly in the insulation depth calculation: Required Depth = Target R-Value ÷ R-Value per inch (by material). This is an exact calculation based on the chosen insulation material.
Used in: Attic insulation calculator — required depth and bag/roll quantity calculation
The 1:150 ventilation ratio (one square foot of net free vent area per 150 sq ft of attic floor, or 1:300 with vapour barrier) is specified in the International Residential Code (IRC) and adopted widely across multiple jurisdictions. This is the basis of our attic ventilation calculator. The 50/50 intake/exhaust split is specified in IRC R806.2. Local codes may differ — always verify with your local building authority.
Used in: Attic ventilation calculator — required NFVA calculation and vent quantity output
Coverage rates per bag of blown-in insulation and per roll of batt insulation are sourced from technical data sheets published by major insulation manufacturers. We use conservative (lower) coverage rates to avoid underestimating quantity. These rates assume properly compacted installation at the target depth.
Used in: Bags/rolls required output in attic insulation calculator
Asphalt Millings Calculator — Data Sources
Volume and weight calculations in the asphalt millings calculator use published material engineering values.
Density of compacted recycled asphalt pavement (RAP) / asphalt millings is approximately 110–135 lbs/cubic foot (1,760–2,160 kg/m³) depending on gradation and aggregate type. Loose millings have a compaction factor of approximately 0.85–0.90 (they compact to 85–90% of loose volume). These values are used to convert area × depth inputs to volume and weight outputs. Sources include published pavement engineering manuals and state DOT material specifications.
Used in: Volume (yd³/m³) and weight (tonnes) output; compaction factor applied to loose → compacted conversion
Master Formula Reference Table
Every deterministic formula used across all calculators, with the source standard or reference.
| Calculator | Output | Formula | Source Standard |
|---|---|---|---|
| Lumber | Board feet | (T_in × W_in × L_ft) ÷ 12 | Industry standard board-foot measure |
| Lumber | Weight | BF × Density (lbs/BF by species) | USDA Wood Handbook |
| Attic Insulation | Required depth | Target R-Value ÷ R/inch (by material) | ASHRAE / manufacturer data |
| Attic Insulation | Bags required | Area × Depth ÷ Coverage per bag | Manufacturer technical data |
| Attic Ventilation | Required NFVA | Attic Area ÷ 150 (or ÷ 300 with VB) | IRC Section R806 |
| Attic Ventilation | Intake / exhaust split | Each = NFVA ÷ 2 | IRC R806.2 |
| Asphalt Millings | Volume (yd³) | (L_ft × W_ft × D_in ÷ 12) ÷ 27 | Standard volumetric conversion |
| Asphalt Millings | Weight (tons) | Volume_yd³ × Density_tons/yd³ | Pavement engineering references |
| House Build Cost | Estimated cost range | Area × BaseRate × QualityMult × ComplexityMult | Published cost indices (see above) |
Known Data Gaps & Limitations
We are committed to showing where the data is strong and where an estimate requires more local validation.
Not every country has a verified local residential construction profile. Countries without sufficient local evidence use the fallback planning index and should be checked carefully against local contractor bids and supplier pricing.
Rural, metro, high-cost, and remote multipliers help reflect within-country differences, but they are broad planning categories. They do not represent a live quote for a specific city, postal code, contractor, or site.
Construction pricing can move faster than published research during inflation, material shortages, labor constraints, or sudden supply-chain changes. Exchange rates may refresh more frequently than construction-cost profiles, but fresh FX does not make the underlying construction data real time.
House-build pricing profiles are residential-focused. Commercial construction has different structural systems, labor arrangements, compliance requirements, procurement practices, and contractor pricing. Do not use the residential house calculator for commercial project budgeting.
Suggest a better data source. If you work in construction estimating and believe a source would improve a country profile or formula, we welcome submissions. See our Editorial Policy — Contact section.