Cost Estimation Methodology
Data sources, calculation formula, worked example, and known limitations
1. Data Sources
Every estimate draws on five public or industry-standard data sets. The table below shows exactly what each source contributes, at what geographic resolution, and when it was last refreshed in our model.
| Source | What It Contributes | Geography | Update Cadence | Model Role | Last Refreshed |
|---|---|---|---|---|---|
| BLS OEWS | Hourly and annual wages for construction occupations (roofers, electricians, plumbers, HVAC mechanics, etc.) | State-level | Annual (May release) | Sets per-state labor cost components | April 2026 |
| Craftsman National Estimator | Material unit costs, labor productivity rates, and installed assembly prices from 10 Craftsman cost databases | National (with per-ZIP area modifiers) | Annual (quarterly cloud updates) | Material rates, labor hours, equipment costs | April 2026 |
| Craftsman Markup & Profit | Remodeling contractor overhead and profit markup (1.50x multiplier on direct costs) | National | Annual | Overhead + profit multiplier | April 2026 |
| BEA Regional Price Parities | State-level goods price indices for localizing national material costs | State-level | Annual | State material cost adjustment factor | April 2026 |
| BLS Producer Price Index | Inflation adjustment for construction materials between annual Craftsman releases | National | Monthly | Material cost inflation adjustment | April 2026 |
2. How Estimates Are Built
Construction calculators follow a five-step formula. The inputs change by project type (roofing uses square footage, HVAC uses system tonnage), but the structure is consistent. Non-construction calculators (childcare, insurance, home warranty) use survey-based pricing models instead.
Material cost per unit
Drawn from Craftsman National Estimator cost databases, adjusted by BEA Regional Price Parities for state-level localization. Varies by material type (e.g., asphalt shingles vs. metal roofing) and by state.
Labor cost per unit
BLS OEWS hourly wages for the relevant occupation, converted to per-unit cost using Craftsman productivity rates. State-specific.
Project size and condition multipliers
Combined cost is multiplied by project size (e.g., 2,000 sq ft), then adjusted by condition factors. For roofing: pitch multiplier and story multiplier. For kitchens: layout complexity. These multipliers are documented in the calculator data files.
Overhead multiplier
Covers contractor profit, insurance, equipment, waste, and business costs. Based on Craftsman Book Company's remodeling markup guide (1.50x multiplier on direct costs). Applied as 50% on construction subtotal.
Permit costs
Added as a percentage of construction cost, based on NAHB survey data. Percentage varies by state, typically 1.5%-3.5% of construction cost.
Low / Mid / High range
The range is derived from Craftsman cost data, which reports three price points for each line item: the 25th percentile (p25), the interquartile mean (IQM), and the 75th percentile (p75). The low estimate uses p25 rates throughout, mid uses IQM rates, and high uses p75 rates. This means the spread reflects actual price variation in the Craftsman dataset, not a fixed multiplier.
3. Worked Example
The following walks through a real calculation to show exactly how the formula produces an estimate.
Project: 1,800 sq ft roof replacement in Texas
Asphalt shingles, moderate pitch (4:12 to 6:12), single-story home
| Step | Calculation | Amount |
|---|---|---|
| Material cost (IQM) | $3.85/sq ft × 1,800 × 0.986 RPP | $6,832 |
| Labor cost | $0.33/sq ft × 1,800 × 1.44 burden | $855 |
| Pitch multiplier | × 1.0 (moderate pitch) | no change |
| Story multiplier | × 1.0 (single story) | no change |
| Subtotal | $6,832 + $855 | $7,687 |
| Overhead + profit (50%) | $7,687 × 0.50 (Craftsman markup) | $3,844 |
| Permits (1.8%) | $7,687 × 0.018 (NAHB state %) | $138 |
| Mid estimate | subtotal + overhead + permits | $11,669 |
Low Estimate
$10,296
same project, p25 material rates
Mid Estimate
$11,669
same project, IQM material rates
High Estimate
$12,909
same project, p75 material rates
4. Childcare, Insurance, and Home Service Estimates
The five-step formula above applies to home improvement projects where labor, materials, and permits drive the cost. Our childcare, insurance, and home service calculators work differently — they report surveyed prices directly rather than computing estimates from component costs.
Childcare
State-level annual childcare costs come from the Child Care Aware of America (CCAoA) 2024 survey data. The survey reports median annual costs by care type — infant center, toddler center, preschool, and family home — for each state. We display these figures directly. No formula is applied.
Renters Insurance
State-level annual premium data comes from industry rate surveys. Each state has a single annual premium figure reported directly from the survey with no additional calculation.
Home Warranty and Home Security
These calculators show published provider plan pricing organized into low, mid, and high tiers by coverage level. Monthly costs are converted to annual figures for comparison. Pricing comes from provider rate sheets and industry surveys.
All data sources, geographic coverage, and last-refreshed dates are listed on our data sources page.
5. State Adjustments
National averages are misleading for home improvement costs. We maintain separate cost profiles for all 50 states, each with its own labor rates, material costs, permit fees, and overhead factors.
Labor rates
Set per state from BLS OEWS data. A roofer in California earns roughly 40% more per hour than a roofer in Texas, and this flows directly into per-sq-ft labor cost.
Material costs
Regional pricing from Craftsman cost databases, adjusted by BEA Regional Price Parities. Transportation distance, local demand, and supply chain factors create differences of 10-25% between states.
Permit fees
Modeled as a percentage of construction cost based on NAHB survey data. States with stricter building codes (California, Florida, Massachusetts) typically have higher permit percentages and more inspection requirements.
Overhead factors
Insurance rates, workers' compensation, and business costs vary by state. High-cost states tend to have higher overhead multipliers.
Comparison: same project, different states
The 1,800 sq ft asphalt shingle roof replacement from the worked example costs approximately $11,669 in Texas but approximately $16,900 in California. The difference is driven primarily by higher labor rates, stricter permitting requirements, and higher contractor overhead in California. For states with large internal variation (California, Texas, New York), our estimates reflect statewide averages. Actual costs in high-cost metro areas may exceed the estimate, while rural areas may come in lower.
6. Limitations
These estimates are planning tools, not contractor bids. The following conditions are not modeled and can cause actual costs to differ from our estimates.
| Limitation | Impact |
|---|---|
| Standard access conditions assumed | Steep lots, narrow driveways, multi-story scaffolding, and limited equipment access add 10-30% to labor costs. Not captured in our estimates. |
| Hidden damage in older homes | Water damage, rotted sheathing, mold, outdated wiring, and structural problems are discovered during work. These change scope and cost unpredictably. |
| Intra-state variation | Metro areas within a state can vary 20-30% from the state average. A roof in San Francisco costs substantially more than the same job in Fresno, though both use the California rate. |
| Seasonal pricing fluctuations | Contractor pricing varies by season and local demand. Peak seasons (spring/summer in northern states, post-hurricane in southern states) can add 10-20%. Not modeled. |
| Custom and architectural work | Custom designs, unusual materials, historical preservation requirements, and non-standard specifications are outside the scope of these calculators. |
| Contractor-specific pricing | Individual contractors price based on their current workload, overhead structure, and competitive strategy. Two equally qualified contractors in the same zip code may quote 20% apart. |
Always obtain multiple quotes from licensed, insured contractors in your area before committing to a project. Use our estimates as a starting point for budgeting and for evaluating whether a quote is in a reasonable range.
7. Update Process
When a calculator displays "2026 data," it means the following update cycle has been completed.
| Data Component | Review Frequency | Trigger |
|---|---|---|
| Full data review | Annually | January each year. All sources re-pulled, all calculators re-validated. |
| BLS wage data | Annually | Applied when new OEWS release is published (typically March-April). |
| Material pricing (BLS PPI) | Monthly | BLS Producer Price Index checked monthly for inflation adjustment. |
| Permit percentages (NAHB) | Annually | Permit cost as percentage of construction cost, from NAHB survey. |
Last Full Refresh
April 2026
Methodology Version
2.0
7. Corrections
If you believe an estimate is significantly off for your area, report it. We review every correction report and use them to identify data gaps and calibration errors in our state-level models.
Include: the calculator used, your state, the estimate you received, and what you believe the actual cost should be (with source if available).