What a layout calculator outputs
Beyond total riser and tread numbers, a stringer layout calculator gives you the framing-square settings (the riser measurement on the tongue, the tread measurement on the body), the number of times to step the square down the board, and the adjustments at the top and bottom cut that a raw riser/tread table doesn't show on its own.
Setting the framing square
A framing square has two arms: the tongue (shorter, usually 16-24in) and the body (longer, usually 24in). Clamp stair gauges or fasten stops to the square at your riser measurement on the tongue and your tread measurement on the body — for a 7.71in riser and 10in tread, set gauges at 7.71in and 10in respectively. Lay the square against the edge of the stringer board with both gauges touching the edge, and trace along both arms to mark one riser line and one tread line.
- Set stair gauges on the square at the riser figure (tongue) and tread figure (body).
- Place the square at the top of the stringer board, gauges against the top edge.
- Trace the riser line (vertical cut) and tread line (horizontal cut) for the first step.
- Slide the square down so the previous tread line's endpoint becomes the new starting point, and repeat.
- Repeat once for each tread — one fewer time than the total riser count, since the last riser meets the upper floor.
Top and bottom cut adjustments
The layout doesn't simply repeat the same riser/tread step from top to bottom — the bottom of the stringer is typically shortened by the thickness of the tread board (or riser board, depending on framing method), so that once the tread stock is installed, the first step's actual riser height matches all the others. Skipping this adjustment is one of the most common reasons a DIY-built staircase has one riser noticeably different from the rest, usually the bottom one.
| Adjustment | Why it's needed | Typical amount |
|---|---|---|
| Bottom cut shortened | Compensates for the added tread board thickness at the first step | Equal to tread board thickness, commonly about 1-1.5in |
| Top cut adjusted | Aligns the top tread with the finished upper floor level | Depends on framing method and header position |
| Notch for ledger/header at top | Seats the stringer against the upper floor framing | Sized to the specific header/ledger detail |
The bottom step is the one that usually comes out wrong
If a built staircase has one step noticeably taller or shorter than the rest, it's almost always the bottom step, because the bottom-cut adjustment for tread board thickness was missed or miscalculated. Double-check this adjustment before cutting the first stringer.
Worked example: full layout for 14 risers
Riser 7.71in, tread 10in, 14 risers, 13 treads (straight flight).
| Layout element | Value |
|---|---|
| Framing square tongue setting (riser) | 7.71in |
| Framing square body setting (tread) | 10in |
| Number of steps down the board | 13 (one per tread) |
| Bottom cut adjustment | Subtract tread board thickness, commonly ~1in |
| Total stringer length before cuts | √(107.94² + 130²) ≈ 169in (Pythagorean, using 14×7.71 rise, 13×10 run) |
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Open the stair runner calculatorCutting a stringer once it's marked
Cut along the traced lines with a circular saw, stopping just short of the inside corner of each notch to avoid over-cutting into the remaining stringer material, then finish each corner with a handsaw or jigsaw. Over-cutting past the corner weakens the stringer at exactly the point it needs the most strength — a small triangular over-cut is a common and avoidable structural flaw in DIY stringers.
Using the first stringer as a pattern
Once one stringer is cut and test-fitted, use it as a template to trace the remaining stringers rather than remeasuring each one from the layout calculator's numbers again — this guarantees all stringers are identical, which matters more for a level, consistent flight than each one being independently perfectly accurate to the calculator's decimal output.
- Test-fit the first stringer in place before using it as a pattern for the rest.
- Check it against the actual site rise and run, not just the calculator's numbers, in case the site has settled or shifted from the design assumptions.
- Mark the pattern stringer clearly and keep it in case a stringer is damaged later and needs replacing.
Whatever you decide, get the numbers first: the stair runner calculator doubles as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length the first time.
Frequently asked questions
What does a stringer layout calculator add beyond riser and tread numbers?
It gives the framing-square gauge settings for riser and tread, the number of times to step the square down the board, and the top/bottom cut adjustments needed so every step comes out the same height.
How do I set a framing square for stair layout?
Clamp stair gauges to the square at your riser measurement on the tongue and your tread measurement on the body, then trace along both arms with the gauges held against the board's edge.
Why is the bottom stringer cut shorter than the others?
To compensate for the thickness of the tread board added at the first step — without this adjustment, the bottom step ends up taller than the rest once the tread stock is installed.
How many times do I step the framing square down the stringer?
Once per tread, which is one fewer than the total number of risers, since the top riser meets the upper floor directly rather than another tread.
What causes an uneven bottom step on a DIY staircase?
Almost always a missed or miscalculated bottom-cut adjustment for tread board thickness during stringer layout — it's the most common single-step error in hand-built stringers.
Should I cut all stringers separately or use a pattern?
Cut and test-fit one stringer first, then use it as a physical pattern to trace the remaining stringers, which guarantees they're identical rather than each being independently measured.
What happens if I over-cut a stringer notch corner?
Cutting past the inside corner of a notch weakens the stringer exactly where it needs strength. Stop the saw short of the corner and finish it with a handsaw or jigsaw instead.
Do I need a special tool to lay out a stringer, or can I do it by hand?
A basic framing square with stair gauges is the traditional hand method and works fine; a stringer layout calculator just automates the arithmetic so you know the exact gauge settings before you start marking.
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Open the stair stringer calculatorEvery guide is written from hands-on measuring and fitting experience, checked against the calculator’s own maths, and re-reviewed whenever prices or methods change. Read our editorial standards.