Units and conversions
Dimension calculations normalize measurements in meters before computing lengths, square meters, or cubic meters. Conversions include exactly 1 foot = 0.3048 meters; 1 square foot = 0.09290304 square meters; and 1 cubic foot = 0.028316846592 cubic meters. One cubic yard equals 27 cubic feet. For paint, a US liquid gallon equals 3.785411784 liters.
Mathematical conventions
Where materials are sold in whole containers, boards, rolls, posts or boxes, we round purchases upward using a ceiling function. Intermediate arithmetic retains decimal precision. Monetary cost lines are rounded to two decimal places for display and are added to produce the displayed total.
Paint is calculated from net wall surface, coat count, coverage and waste; flooring purchases apply waste to material, not the installed area; tile quantities use a rectangular layout grid including grout separation; concrete uses dimensions normalized to cubic meters; wallpaper uses full-height drops and pattern repeats. The individual calculator page shows its complete formula and exceptions.
Pricing assumptions
Sample prices are centrally stored in the source configuration and are deliberately illustrative. They are not current verified national averages or region-specific observations. Changing currencies changes the labels, not the amount or its real-world market value: we do not compute foreign-exchange conversions.
Any future market-rate dataset must keep region, original source, methodology, date of observation and review date, and must be verified before publication. This release does not have such a dataset, nor does it imply that a ZIP code enables reliable local pricing.
Taxes, contingency, and payments
The kitchen and bathroom planners independently apply contingency and optional tax percentages to the same pre-tax sum of entered categories. The whole-renovation planner computes contingency from its pre-tax subtotal and optional tax only on entered materials plus labor. Tax is never compounded on contingency. Deposits and payments already made reduce remaining payable cash, not the project total.
Safety and uncertainty
Site conditions, installation methods, jurisdictional rules, manufacturer packaging, access, labor availability, price changes, and unforeseen defects may significantly change the final cost. These tools do not evaluate load-bearing capacity, electrical, gas, structural or waterproofing safety. For regulated work, use qualified professionals and check local requirements.
Privacy and local state
Calculations run in your browser. Saved inputs, favorite tools and scenarios use localStorage rather than a user account. They can be erased by clearing the browser's site data. Hosting services may separately retain ordinary access logs; see the privacy page.