# How to Measure a Room for Paint and Drywall Measure each wall and ceiling, subtract openings, handle gables, slopes, and stairwells, and keep it all on one sheet. Guide page: (published 2026-10-05, updated 2026-10-05). This Markdown version has the guide's key points, outline, FAQs and sources; the full article, with its worked examples and diagrams, is on the page. ## Key takeaways - Measure every wall on its own and add them up; a room's perimeter × wall height only works when all walls are the same height. - Record openings (width × height) separately so you can decide later what to subtract for paint and for drywall. - Gable walls are a rectangle plus a triangle; stairwell walls are trapezoids; sloped ceilings are horizontal width × slope factor × length. - Paint needs net area × coats ÷ the coverage on your label; drywall needs gross area plus an allowance, divided by the sheet size. ## In this guide 1. [Tools and a measurement sheet](https://www.howmanyyardsdoineed.com/guides/how-to-measure-a-room-for-paint-and-drywall/#tools-and-a-sheet) 2. [Measure the walls](https://www.howmanyyardsdoineed.com/guides/how-to-measure-a-room-for-paint-and-drywall/#walls) 3. [Measure the ceiling](https://www.howmanyyardsdoineed.com/guides/how-to-measure-a-room-for-paint-and-drywall/#ceilings) 4. [Doors, windows, and other openings](https://www.howmanyyardsdoineed.com/guides/how-to-measure-a-room-for-paint-and-drywall/#openings) 5. [Gable walls](https://www.howmanyyardsdoineed.com/guides/how-to-measure-a-room-for-paint-and-drywall/#gable-walls) 6. [Sloped ceilings](https://www.howmanyyardsdoineed.com/guides/how-to-measure-a-room-for-paint-and-drywall/#sloped-ceilings) 7. [Stairwell walls](https://www.howmanyyardsdoineed.com/guides/how-to-measure-a-room-for-paint-and-drywall/#stairwells) 8. [Worked example: one room, start to finish](https://www.howmanyyardsdoineed.com/guides/how-to-measure-a-room-for-paint-and-drywall/#worked-example) 9. [Turning measurements into paint and drywall](https://www.howmanyyardsdoineed.com/guides/how-to-measure-a-room-for-paint-and-drywall/#paint-vs-drywall) ## Frequently asked questions ### Should I measure in feet or inches? Measure in feet and inches, then convert to decimal feet before multiplying: 8 ft 6 in is 8.5 ft, and 7 ft 4 in is about 7.33 ft. Mixing feet and inches in one multiplication is the most common source of errors. ### How do I find the area of a gable wall? Treat it as a rectangle plus a triangle. The rectangle is the wall width × the height to the top of the straight wall. The triangle is ½ × the wall width × the extra height from there to the peak. Add the two. ### Should closets be included? Yes, if you are painting or hanging drywall in them. Measure each closet as its own small room with its own walls, ceiling, and door opening, and add it to the sheet as a separate line. ### How precise do my measurements need to be? For estimating quantities, the nearest inch is plenty. Rounding each wall up to the next inch builds in a little margin, and the allowance in the calculator covers cutting and waste. ### How do I measure a ceiling that slopes? Measure the horizontal width the slope covers and its length, find the pitch, and multiply width × slope factor × length. A 6 ft horizontal width at an 8/12 pitch is about 7.21 ft along the slope. ## Related calculators and guides ### Calculators - [Paint Calculator](https://www.howmanyyardsdoineed.com/paint-calculator/) — Gallons or liters of paint for your walls and number of coats, using the coverage printed on your paint's label. - [Drywall Calculator](https://www.howmanyyardsdoineed.com/drywall-calculator/) — Drywall sheet count for walls and ceilings from room dimensions or total area, minus openings, by sheet size. - [Square Footage Calculator](https://www.howmanyyardsdoineed.com/square-footage-calculator/) — Total area in square feet, square meters, square yards, and acres from rectangles, triangles, circles, and trapezoids, minus cut-outs. - [Roof Pitch Calculator](https://www.howmanyyardsdoineed.com/roof-pitch-calculator/) — Pitch as x/12, roof angle in degrees, slope percentage, and the sloped length for a given horizontal run. ### Guides - [How to Measure an Irregular Area](https://www.howmanyyardsdoineed.com/guides/measuring-irregular-areas/) — Split odd shapes into rectangles, triangles, circles, and trapezoids, then average width and depth. - [Tile Layout Patterns and How They Change Your Order](https://www.howmanyyardsdoineed.com/guides/tile-layout-patterns/) — Common tile patterns, the industry offset and grout joint rules for large tile, centering a layout, and overage by pattern. ## Sources - [USG Sheetrock Brand UltraLight Panels submittal sheet (WB2501)](https://www.usg.com/content/dam/USG/pdpmovedocuments/sheetrock-ultralight-panels-submittal-en-wb2501.pdf) — USG Corporation. Used for: Width 4 ft or 54 in; lengths 8–16 ft. Checked 2026-10-03. - [Benjamin Moore Regal Select Interior Paint & Primer, Eggshell (N549) technical data sheet](https://media.benjaminmoore.com/WebServices/prod/assets/stage/datasheets/TDS_0549/N549_TDS_US.pdf) — Benjamin Moore & Co.. Used for: 400–450 sq ft per gallon at the recommended film thickness. Checked 2026-10-03. - [NIST Guide to the SI, Appendix B.9: Factors for units listed by kind of quantity](https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b9) — National Institute of Standards and Technology. Used for: 1 ft = 0.3048 m (exact); 1 in = 2.54 cm (exact). Checked 2026-10-03. **Estimate only.** Results are planning estimates computed from the numbers you enter. They are not engineering, structural, or code advice. Confirm quantities, product yields, and installation requirements with your supplier, the product label, and your local building authority before you order or build.