# How to Lay Out Stairs: Rise, Run, and Stringers From total rise to equal risers, tread depth, total run, and a marked-out stringer, with a worked example. 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 the total rise from finished surface to finished surface at the spot where the stair lands. - Divide the total rise by your maximum riser height and round up: that is the number of risers, all made equal. - There is one fewer tread than risers; total run is treads × tread depth. - The stringer's diagonal is √(total rise² + total run²); buy boards longer than that for the end cuts. - The 2018 IRC, as quoted in a municipal guide, limits risers to 7-3/4 in and treads to at least 10 in; check your local code. ## In this guide 1. [The parts of a stair](https://www.howmanyyardsdoineed.com/guides/stair-layout-basics/#parts-of-a-stair) 2. [Measure the total rise](https://www.howmanyyardsdoineed.com/guides/stair-layout-basics/#measure-total-rise) 3. [Work out risers and treads](https://www.howmanyyardsdoineed.com/guides/stair-layout-basics/#risers-and-treads) 4. [Worked example: a 9 ft floor-to-floor stair](https://www.howmanyyardsdoineed.com/guides/stair-layout-basics/#worked-example) 5. [Marking a stringer](https://www.howmanyyardsdoineed.com/guides/stair-layout-basics/#marking-a-stringer) 6. [Code limits to check](https://www.howmanyyardsdoineed.com/guides/stair-layout-basics/#code-limits) 7. [Common layout mistakes](https://www.howmanyyardsdoineed.com/guides/stair-layout-basics/#common-mistakes) ## Frequently asked questions ### Why is there one fewer tread than risers? Each riser lifts you to a tread, except the last one, which lifts you onto the upper floor or deck. So a straight stair with 15 risers has 14 treads. ### Should I round the number of risers up or down? Up. Rounding up guarantees that no riser is taller than your maximum. Rounding down would make every riser taller than the height you chose. ### How do I account for flooring that isn't installed yet? Measure to the finished surfaces. If the bottom floor will get thicker flooring than the top, the first riser comes out shorter than the rest, so plan for both finishes before cutting stringers. ### What is the stringer length for a stair? The diagonal is the square root of total rise squared plus total run squared. For a 108 inch rise and a 140 inch run it is about 176.8 inches, or 14 ft 8-13/16 in, before allowing for the end cuts. ### What are the riser and tread limits? The 2018 International Residential Code, as quoted in the Town of Timnath's residential stair guide, sets a 7-3/4 inch maximum riser, a 10 inch minimum tread, and no more than 3/8 inch variation within a flight. Local codes may differ. ## Related calculators and guides ### Calculators - [Stair Calculator](https://www.howmanyyardsdoineed.com/stair-calculator/) — Number of risers and treads, exact riser height, total run, stair angle, and stringer length from floor-to-floor rise. - [Deck Calculator](https://www.howmanyyardsdoineed.com/deck-calculator/) — Decking board count from deck size, actual board width, gap, and board length, with the cutting assumptions shown. - [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. - [How to Plan a Bulk Material Delivery](https://www.howmanyyardsdoineed.com/guides/planning-material-delivery/) — Rounding to supplier increments, questions to ask, and a checklist before bulk material arrives. - [Nominal vs. Actual Lumber Sizes](https://www.howmanyyardsdoineed.com/guides/nominal-vs-actual-lumber-sizes/) — A chart of real lumber dimensions from the national standard, dry versus green sizes, lengths, and board feet. ## Sources - [2018 Residential Stair Guide (IRC Section R311.7), SAFEbuilt Colorado, published by the Town of Timnath](https://timnath.org/wp-content/uploads/2022/03/2018-RESIDENTIAL-STAIR-GUIDE.pdf) — Town of Timnath, Colorado / SAFEbuilt Colorado. Used for: Max riser 7-3/4 in; min tread 10 in; nosing 3/4–1-1/4 in with solid risers (not required if tread ≥ 11 in); headroom 6 ft 8 in; max 12 ft rise per flight. Checked 2026-10-05. - [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.