How we estimate costs
Every HouseMath calculator is built the same way, so you can compare projects on equal terms.
1. Installed price per unit
For each option on a page, such as a roofing material or a water heater type, we maintain a low and high installed price. Installed means materials and labor together. Prices are per the unit contractors quote in: square feet, linear feet, tons, fixtures or the whole job.
2. Adjustments for your conditions
Some conditions change labor time for the whole job, such as roof pitch, number of stories or site access. The calculator applies these as a percentage adjustment to the base price.
3. Add-ons and fixed costs
Extras you tick, such as removing an old installation or adding a gate, are added on top. Where a job almost always carries fixed costs, such as a permit or disposal, those are included and listed separately.
4. The range and the midpoint
The low end fits a simple job with standard materials in a lower-cost area. The high end fits a complex job, premium brands or a high-cost metro area. The large number on each calculator is the midpoint of your range.
How we check and update figures
We compare our ranges against current installer, manufacturer and retailer pricing, and we use U.S. Bureau of Labor Statistics wage data to understand how trade labor costs differ by state. Each page shows the date its figures were last reviewed, and that date changes only when the content changes.
Limits of any estimate
No calculator can see your house. Hidden damage, local codes, permit fees and contractor availability all affect real prices. Use HouseMath ranges to plan and to compare quotes, then rely on written quotes from licensed local professionals.
Spotted a price that looks off for your area? Tell us at hello@housemathguide.com.