A practical starting point for decorative trim.

Picture-frame molding

The planner subtracts the two side margins and the gaps between frames from the treatment width, then divides the remaining space equally among the columns. It applies the same method to the height, top and bottom margins, vertical gaps, and rows.

The resulting frame dimensions are outside dimensions. Each frame needs two horizontal pieces at its outside width and two vertical pieces at its outside height, measured long point to long point for 45-degree miters. Subtracting twice the trim face width gives each clear inside dimension.

For example, a 144-inch-wide area with 6-inch side margins, three frames, and 6-inch gaps gives (144 − 12 − 12) ÷ 3 = 40 inches of outside width per frame. With 2.5-inch trim, each clear opening is 35 inches wide.

Board & batten

This is a decorative trim layout over an existing surface. The top and bottom rails span the full treatment width. Vertical battens sit at both edges and between each equally sized clear bay; they fit between the two rails.

For three clear bays, the layout uses four vertical battens. The clear bay width is the treatment width minus those four batten widths, divided by three. Each batten's cut length is the treatment height minus the top and bottom rail widths.

It does not calculate exterior siding, backing boards, structural framing, or a weather-resistant wall assembly.

Wainscoting

The wainscoting layout uses full-height vertical stiles at the edges and between columns. Horizontal rails fit between those stiles at the top, bottom, and each row boundary.

The planner subtracts the combined stile widths before dividing the remaining width into equal panels. It subtracts the combined rail widths before dividing the remaining height into equal panel rows. Each horizontal rail is cut to the clear width between adjacent stiles.

All rails and stiles use the same entered face width. The cut list assumes square ends. Different joinery, unequal trim widths, caps, backing panels, and existing baseboards require separate measurements and planning.

What the calculator checks

The calculator rejects invalid dimensions and layouts with no positive clear panel space. You can add one rectangular keep-clear area to check whether the proposed trim overlaps it. That check highlights overlap but does not automatically move or shorten pieces.

Inches and centimeters describe the same layout. Fraction inputs such as 3 1/2 are accepted. Displayed cut lengths are rounded to 0.001 inch or 0.01 centimeter; the drawing is a scaled reference, not a full-size cutting template.

What to check on the real project

Walls can be uneven or out of square. Measure the usable treatment area in several places, use the actual face width of your trim, and mark the layout on the wall before cutting. Inspect every obstacle, including any that are not represented by the single keep-clear rectangle.

The material target adds your selected percentage to the total linear cut length. It does not optimize pieces onto stock boards or guarantee a board count. Saw kerf, end trimming, defects, grain preferences, joint details, and available stock lengths can change the amount you need to buy.

The planner does not assess fastening, wall condition, electrical work, structural suitability, or building requirements. Use it to develop a layout and verify the dimensions against the actual job.