AngleWise / Stairs
How to Build Stairs:
Rise, Run & Stringer Angles
Stairs come down to a little triangle repeated over and over. Tell the calculator your total rise and the run you want, and it hands you the number of steps, the exact stringer cut angle, and what to set your saw to — no trig required.
Stair Calculator
The Terms, In Plain English
Total Rise
The whole vertical height your stairs climb — measured from the finished floor at the bottom to the finished floor at the top. This is the single most important number.
The whole vertical height your stairs climb — measured from the finished floor at the bottom to the finished floor at the top. This is the single most important number.
Rise (per step)
How tall each individual step is. Comfortable is about 7 to 7¾ inches. Every step should be the same height — uneven steps are what trip people.
How tall each individual step is. Comfortable is about 7 to 7¾ inches. Every step should be the same height — uneven steps are what trip people.
Run / Tread (per step)
How deep each step is front to back — where your foot lands. Usually 10 to 11 inches.
How deep each step is front to back — where your foot lands. Usually 10 to 11 inches.
Stringer
The sawtooth-cut board on the side that carries the steps. The angle you cut it at is the same as the angle of the whole staircase.
The sawtooth-cut board on the side that carries the steps. The angle you cut it at is the same as the angle of the whole staircase.
How to Figure Your Stairs, Step by Step
- Measure your total rise from finished floor to finished floor. Get this exact — everything else builds off it.
- Find your number of steps. Divide total rise by a comfortable step height (around 7.5"). Round to the nearest whole number. That's how many risers you'll have.
- Get your actual step rise. Divide total rise by that whole number of steps. It'll land close to 7.5" — and now every step is equal.
- Pick your run. 10 to 11 inches per tread is the comfortable range. Deeper runs eat more floor space; shorter runs feel steep.
- Mark and cut the stringer. Use the cut angle from the calculator above. The plumb (vertical) cut and the level (seat) cut come straight from your rise and run.
Code & Comfort Rules of Thumb
Two quick guidelines keep stairs feeling right under foot:
- Keep rise between about 7 and 7¾ inches and run between about 10 and 11 inches for residential stairs.
- The old carpenter's comfort check: two times the rise plus the run should land around 24 to 25 inches. A 7.5" rise with a 10" run gives 25 — right in the pocket.
Always check your local building code. Rise and run limits, headroom, and railing rules vary by area and can change. The numbers here are general comfort guidelines, not a substitute for the code that applies where you're building.
Common Mistakes
- Forgetting tread thickness. The finished tread and flooring change your first and last step heights. Measure floor-to-floor finished, and adjust the bottom riser for the tread you'll add.
- Uneven step heights. If the top or bottom step is off by even a half inch, people stumble. Dividing total rise evenly across whole steps prevents it.
- Eyeballing the angle. Cutting the stringer by guess instead of off the actual rise and run leads to steps that aren't level. Mark it from the numbers.
- Too steep to save space. Cramming in fewer, taller steps to fit a tight spot makes a staircase that's tiring and unsafe. Respect the comfortable ranges.
Frequently Asked Questions
- How many steps do I need for a given total rise?
- Divide your total rise by about 7.5 inches and round to the nearest whole number. For example, 108 inches divided by 7.5 is roughly 14 steps, which gives an actual step rise near 7.7 inches. The calculator above does this for you.
- What is a comfortable stair angle?
- Most comfortable staircases fall between about 30 and 37 degrees. Steeper starts to feel like a ladder; shallower uses up a lot of floor.
- What is the rule for stair rise and run?
- A common comfort guideline is that two times the rise plus the run equals roughly 24 to 25 inches, with rise around 7 to 7¾ inches and run around 10 to 11 inches.
- Do I need to account for tread thickness?
- Yes — measure total rise from finished floor to finished floor, and adjust the bottom riser for the thickness of the tread and flooring so your first and last steps come out even.
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