How we estimate

Last updated October 2026

Every CostWise Lab calculator follows the same three steps.

1. Your measurements

We start from the numbers you enter: length, area, pitch or thickness. Geometry is calculated exactly. For example, roof area uses the Pythagorean theorem and concrete volume uses standard volume formulas.

2. Published 2026 price ranges

For cost calculators, we compile national installed price ranges (materials and labor) from several published 2026 cost guides and list them on each calculator page. We use a low and a high value instead of a single average, because real quotes vary with the contractor, the season and the site.

3. State adjustment

We scale the national range using the Regional Price Parities published by the U.S. Bureau of Economic Analysis (2024 data, via FRED). An index of 110 means prices in that state are about 10% above the national average. Construction costs follow this index only loosely, so the adjustment is an approximation.

Limits

• Estimates are planning ranges, not quotes.
• They exclude permits, removal of old materials, repairs found during the work and unusual site conditions unless stated.
• Always get several written quotes from licensed, insured contractors.

Updates

We review all price ranges at least once a year and whenever our sources publish significant changes. Each page shows its last update date.