Wainscoting calculator
Plan picture frame molding wainscoting below a chair rail, with an optional second row of boxes above it. Set the margins and a target box size; WallVive makes every box equal, lists where each one goes, and turns the layout into a mitred cut list and a count of molding and chair rail sticks.
Fix the margins, and the boxes size themselves.
Set the gap at each end, between boxes, and above and below them. The calculator finds the box count nearest your target width, sizes every box equally, and lists each mitred piece and the molding sticks to buy.
Worked example
A 150 in wall takes 4 boxes of 32 1/2 in × 22 in.
A 3½ in baseboard, a chair rail topping out at 36 in with a 2½ in face, 4 in margins and gaps all round, 1¼ in molding, and a 30 in target box width.
Prefills the calculator below. Your measurements stay in this browser tab.
- 1 · Count4.29 → 4 boxes(150 − 2 × 4 + 4) ÷ (30 + 4), rounded to the count nearest 30 in.
- 2 · Size32 1/2 in wide(150 − 8 − 3 × 4) ÷ 4. Height: 36 − 2½ − 3½ − 8 = 22 in.
- 3 · Buy6 sticks of molding36.33 ft in 16 mitred pieces on 8 ft sticks, plus 10% spare.
The example is one run between corners. Lay out each wall, and each section between door casings, on its own.
Layout drawing
Elevation of the run as you face it, left end on the left. It redraws as you change any input.
Marking list
Outside edges of each box, measured from the left end of the run and up from the floor. Rounded to the nearest 1/16 in.
| Box | Left edge | Right edge |
|---|---|---|
| 1 | 4 in | 35 in |
| 2 | 39 in | 70 in |
| 3 | 74 in | 105 in |
| 4 | 109 in | 140 in |
- Lower boxesbottom 7 1/2 in, top 29 1/2 in
Molding cut list
5 sticks of 8 ft in the plan, plus 1 spare. Buy 6.
- 2 sticks: cut 3 × 31 in lower boxes · width; offcut 2 1/4 in each
- 1 stick: cut 2 × 31 in lower boxes · width + 1 × 22 in lower boxes · height; offcut 11 1/4 in
- 1 stick: cut 4 × 22 in lower boxes · height; offcut 7 in
- 1 stick: cut 3 × 22 in lower boxes · height; offcut 29 1/4 in
Chair rail cut list
2 sticks of 8 ft in the plan, plus 1 spare. Buy 3.
- 1 stick: cut 1 × 96 in chair rail; no offcut
- 1 stick: cut 1 × 48 in chair rail; offcut 47 3/4 in
Dry-fit one box before cutting the rest, and check the molding profile, the wall's flatness, and your fixings. Caulk the inside edges and paint the wall and molding together so the boxes read as part of the wall.
Method and sourcesHow the boxes are sized
The gaps are fixed. The boxes take what is left.
Picture frame wainscoting looks built-in when every gap matches: the same distance from each corner, between each box, and above and below. So the calculator fixes those gaps first and shares the remaining width equally between the boxes. Box width is never rounded during the calculation, which keeps the final gap at the right-hand corner equal to the first.
Sizes are outside dimensions, the long point of each mitred piece. The inside opening is the outside size minus the molding width on both sides, which is why a wide molding needs a wider box to keep the same open panel.
Box count
(run − 2 × end gap + gap) ÷ (target width + gap), rounded to the whole number whose box width is nearest the target.
Box width
(run − 2 × end gap − (boxes − 1) × gap) ÷ boxes, kept unrounded.
Box height
Chair rail top − chair rail face − baseboard − 2 × the gap above and below.
Molding to buy
Four long-point pieces per box packed onto your stick length with a cut allowance, plus spare sticks rounded up.
What this calculator does not decide
It lays out one straight run at a time and does not handle stair walls, sloped ceilings, or boxes that change size across a wall. It does not choose adhesive or fixings. For vertical battens instead of boxes, use the board and batten calculator, and to paint the finished wall, the paint calculator. The full method is on the methodology page.
Wainscoting layout questions
Answers about box layouts and buying molding. The profile you buy and the wall you have still control the final layout.