Estimator methodology
How We Estimate Project Costs
Our calculators and guides are designed for homeowner planning: national-average baselines, transparent multipliers, and explicit assumptions. They are not substitutes for site-specific contractor quotes.
How calculators work
Each tool starts from a baseline rate per unit (such as per square foot or linear foot). Your size input scales the project proportionally. Selectable options apply material and scope multipliers drawn from typical installed-cost relationships, not real-time supplier pricing.
How multipliers apply
Multipliers adjust the baseline when you change materials or scope toggles (for example, metal roofing versus asphalt, or tear-off versus overlay). They are simplifications—actual bids may diverge based on brand, warranty, and site conditions.
Why ranges exist
Contractor overhead, crew efficiency, code-driven upgrades, and scheduling all move final pricing. Low, typical, and high outputs bracket that uncertainty so you can stress-test the budget before you invite bids.
How to interpret estimates
Treat results as orientation: compare them to multiple local quotes, validate assumptions on a walkthrough, and add contingency for unknowns. State pages and future regional adjustments are meant to layer market context on top of national baselines.
For editorial standards and content sourcing, see the broader methodology reference.
Open methodology