Stair Panelling Calculator

Every measurement on a stair panelling job comes from one step. Enter the rise and going of a single step and this calculator gives you the stair angle, the two mitre saw settings you will actually use, the panel sizes up the flight, and the one figure people get wrong: how the gaps open out when you mark them along the slope. It works in mm or inches.

Your flight of stairs
Steps
Panels up the flight
40.4°
Stair pitch40.4°
Saw set to (panel ends)40.4°
Mitre where level meets rake20.2°
Gap marked along the rake131 mm
Panel width (plumb to plumb)393 mm
Raking rail per panel515 mm
Stile (cut plumb)600 mm
Raking dado rail4.01 m
Frame timber to buy14.7 m

6 panels up a 13-step flight climbing 2600 mm over 3055 mm. Timber total includes 10% waste.

Draw this staircase in the planner

or start it in a style: Half Wall · Framed · Board & batten

How to measure your stairs

40.4°the pitchRise200 mmGoing 235 mm, nosing to nosingnosing
Everything comes off one step: the rise, the going, and the line through the nosings they define. The example is the common UK flight of 200 by 235 mm.

You need three numbers: the rise of one step (vertical, tread surface to tread surface), the going of one step (horizontal, nosing to nosing), and the number of risers in the flight. Measure the rise and going on two or three different steps, because on older staircases they vary a little, and use the average. That is the whole survey; you do not need to measure the slope itself, and you do not need an angle gauge.

The nosing is the front edge of each tread. The line through every nosing is the pitch line, and it is the datum everything on a stair wall is measured plumb above: the string, the panels, and the dado rail. A typical modern UK flight is 13 risers of about 200 mm on a 235 mm going, which is a 40.4° pitch climbing 2.6 m between floors. American stairs are built shallower (IRC code allows at most a 7¾ inch riser on a 10 inch minimum tread), so a typical US flight lands between 32° and 37°. The calculator handles either; its steep-flight warning is a UK sanity check, not a US code check.

The two saw settings the calculator gives you

Every cut on a stair panelling job uses one of two mitre saw settings, and both come straight off the pitch: the full pitch for the ends of raked pieces, and half the pitchwhere a level run meets a raking one. On the common 40.4° flight that is a 40.4° setting and a 20.2° setting, and both are comfortably within an ordinary mitre saw's range. Which joint takes which cut, with diagrams of both, is covered in the stair panelling guide; the calculator's job is to give you your own two numbers.

Stair angles for common step sizes

A quick reference across the range domestic stairs are built in, US and UK. American steps are shallower by code (at most a 7¾ inch riser on a 10 inch tread), so US flights cluster at the top of the table; a new UK stair is built to 42° or less, and older flights, lofts, and cottages run steeper. The last column is a 100 mm gap opened out along the slope, which is what a tape lying on the rake reads.

Rise × goingPitch (panel ends)Knee mitre (level meets rake)100 mm gap on the rake
7" × 11" (typical US)32.5°16.2°119 mm
7½" × 10½" (US)35.5°17.8°123 mm
190 × 250 mm (UK)37.2°18.6°126 mm
7¾" × 10" (US code limit)37.8°18.9°127 mm
200 × 235 mm (typical UK)40.4°20.2°131 mm
205 × 225 mm (UK, near limit)42.3°21.2°135 mm
220 × 220 mm (steep, older UK)45.0°22.5°141 mm

Setting out the panels: plumb lines, not the slope

Stair panels are set out between plumb (vertical) lines, spaced horizontally, exactly as they would be on a flat wall. The sides of every panel stay vertical; only the top and bottom rails lean with the stairs, which turns each panel into a parallelogram. That is the whole trick of the classic raked look, and it is also why the maths stays simple: panel widths and gaps are horizontal measurements.

The trap is the tape. A gap that is 100 mm wide horizontally covers about 131 mm measured along a 40° slope, so if you mark your horizontal figures with the tape lying on the rake, every gap comes out narrow and the last panel finishes short of the top. Either mark gaps against a level, or use the along-the-rake figure the calculator gives and mark on the slope deliberately.

Draw the whole staircase wall

The calculator solves one raking run. The free planner draws your whole stair wall to scale: the flight climbing between the hall and the landing, the string the panels stand on, the raking dado rail mitring into the level runs, and panels that stay rectangles where the floor is flat. You can drag panel dividers, change the gap, and get a cut list with every length and saw angle on it. The button under the calculator carries your measured flight straight in, so the planner opens on your staircase, not a sample one, and the style links beside it apply one of the seven ready stair styles at the same time, from the classic Half Wall Stairs band to capped board and batten. The full set is toured in the staircase panelling ideas guide.

Open the Staircase Planner

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Frequently asked questions

What angle do I cut stair panelling at?

There are two different angles, and mixing them up is the most common stair panelling mistake. The ends of every raked piece (the top and bottom rails of the panels, and the vertical stiles where they meet them) are cut at the full stair pitch, typically 35 to 42 degrees. Where a level moulding meets a raking one, like the dado rail turning onto the landing, the joint is mitred at HALF the pitch. The calculator gives you both numbers from the rise and going of one step.

How do I work out my stair angle?

Measure one step: the rise (vertical height from one tread to the next) and the going (horizontal depth from one nosing to the next). The pitch is the angle whose tangent is rise divided by going. A typical UK flight with a 200mm rise and 235mm going comes out at 40.4 degrees. You do not need an angle finder; two tape measurements of a single step are more accurate than most digital gauges held against carpet.

How do you measure for stair panelling?

Measure the rise and going of one step, nosing to nosing, and count the risers. Everything else follows: the pitch sets every angle, and the step count times the going gives the horizontal run of the flight. Measure the rise and going in two or three places, because on older stairs they vary; use the average. Panel heights are measured plumb (straight up), not square to the slope.

Are stair panels parallelograms or rectangles?

On the flight they are parallelograms: the sides stay plumb (vertical) while the top and bottom rails follow the slope of the stairs. Over the hall floor and on the landing they are ordinary rectangles. This is why the classic look works: the vertical lines stay vertical all the way up, and only the horizontals lean with the stairs.

Why is the gap between stair panels longer on the slope?

Because the panels are spaced between plumb lines, a gap measured horizontally covers more distance along the raking line. On a 40 degree flight, a 100mm gap reads about 131mm if your tape is lying on the slope. Mark your gaps as horizontal measurements (or use the along-the-rake figure the calculator gives) or the last panel will come up short.

What angle should a stair dado rail be?

The raking dado rail runs parallel to the stair pitch, so the rail itself sits at the pitch angle, typically 35 to 42 degrees from horizontal. Where it meets the level rail on the landing or in the hall, the two are mitred at half the angle between them, which is half the pitch. On a 40 degree flight that is a 20 degree mitre.

Is this a stair angle calculator for UK building regs?

It tells you your pitch, and it flags a flight that measures steeper than the 42 degrees a new private stair in England and Wales is built to, because that usually means a mistyped measurement. It is a panelling planning tool, not a compliance check: plenty of older staircases genuinely are steeper than current regulations, and panelling them is fine.

Related reading

Wall panelling on stairs: the full guideStaircase panelling ideas and stylesPanelling the hall, stairs and landing as one schemeDado rail height, including on stairs