Picture Frame Moulding Calculator, Done For You

What to Buy and What Tools You Need

You can use any trim sold as “panel moulding,” “base cap,” or “picture frame moulding.” If you are painting your wall, primed MDF or finger-jointed pine are your best bets. Both are smooth, take paint beautifully, and don't have knots that will bleed through your finish.

Once you buy your moulding, measure the actual width of the wood with a tape measure. Store labels are often rounded up. Type that exact number into the calculator (we default to 1 5/8″, a very common size).

Tools for the job:

• A miter saw. You will set this to 45 degrees and leave it there for the entire project.
• A brad nailer. The wood is light, so small pin nails are perfect. Hammering by hand can dent the trim.
• A level. A great layout relies on straight lines.
• Construction adhesive. The glue actually holds the wood to the wall permanently; the nails just hold it in place while the glue dries.
• Finishing supplies. Wood filler, paintable caulk, sandpaper, and paint.

Where the Box Sizes Come From

A professional-looking wall uses the exact same gap size everywhere: between the boxes, above the baseboard, below the ceiling, and at the edges of the wall. The calculator subtracts all those equal gaps from your total wall space, and splits whatever is left into perfectly even boxes. If you leave the “Boxes across” field empty, the app will automatically figure out the best fit, usually boxes around 30 inches wide.

Mark the Wall First

Before you cut any wood, use a pencil and a level to draw your boxes directly on the wall. Floors and ceilings are rarely perfectly level, so always trust your bubble level, not the ceiling line.

DIY tip: cut a small scrap of your moulding to match your exact gap size. Use it as a spacer block between your lines — it is much faster than squinting at a measuring tape forty times.

Every Corner is a 45-Degree Angle

Each box is made of four pieces of wood. Every single end is cut at a 45-degree angle pointing inward, just like a picture frame. The cut list gives you the long point measurement. Just measure from the longest, sharpest tip of the angle to the other. If you are ever unsure, cut the piece a tiny bit long; you can always shave a hair off, but you can't add wood back.

Glue, Nail, and Test Fit

Before gluing anything to the wall, piece your first box together flat on the floor to make sure your corner angles meet up tightly. Once everything looks good, run a thin bead of construction adhesive on the back of the trim, place it on your pencil lines, and shoot a few brad nails in to hold it.

Wipe away any wet glue that squeezes out right away with a damp rag. Dried glue looks like a lumpy mistake under paint and is very hard to sand off.

Fill, Caulk, and Paint

Fill your nail holes with wood filler and gently sand them smooth. Next, run a very thin bead of paintable caulk along the inside and outside edges where the wood meets the drywall, smoothing it with a damp finger. Always caulk before you apply your primer and paint. The caulk hides the shadows and makes the boxes look like they are built into the wall.