How we research and update our guides

Where the numbers come from

• Manufacturer specifications: published dimensions, ratings and care instructions for materials, fixtures and furniture.
• Trade and building standards: published clearance, electrical, wet-zone and fire-safety requirements, cited as general guidance; local codes always take precedence.
• Industry pricing: typical retail and installed price ranges for the US market, stated as ranges rather than single prices.
• Established design practice: the proportion and spacing rules designers use, explained with the reasoning behind them.

How figures are presented

• Dimensions in imperial with metric in brackets, for example 36 in (91 cm).
• Prices in USD as ranges for 2026–2027; installed prices include typical labor unless marked DIY.
• Rules of thumb are labelled as such; where a code or safety requirement applies, the guide says to confirm it locally.
• Every guide opens with a short direct answer and key takeaways, then explains the detail and the exceptions.

Dates and updates

Each guide shows the date it was last updated, and the same date is published in the page’s structured data. Guides are reviewed when prices, standards or products change, and trend guides are rewritten every year. The interior design numbers page collects the key figures from all guides in one table.

Independence

Brands and manufacturers cannot pay to change a recommendation. Guides avoid naming brands and describe products by type and specification. Some shopping links are affiliate links, disclosed on the page and in our affiliate disclosure; sponsored content is always labelled.

Corrections

If you find an error or an out-of-date figure, email [email protected] with the page address. Confirmed corrections are made promptly and the page’s updated date is changed.