Crown Molding Calculator

Measure the perimeter of the room by adding all wall lengths. For rectangular rooms: 2 x (Length + Width). Account for inside and outside corners - each corner requires precise cuts. Measure ceiling height to determine appropriate molding size (3-6 inches for 8-foot ceilings, 5-7 inches for 9-10 foot ceilings). Always add 10-15% waste for cuts, mistakes, and future repairs. Measure twice, cut once!

Room height determines molding size: 8-foot ceilings: 3-4.5 inch molding, 9-foot ceilings: 4.5-6 inch molding, 10+ foot ceilings: 6-8 inch molding. Proportion matters - larger rooms need larger molding. Traditional rule: molding should be 4-6% of wall height. Small molding in large rooms looks cheap. Large molding in small rooms feels heavy. Match existing trim size in adjacent rooms.

Standard waste: 10-15% for experienced installers, 15-20% for DIY projects. Factors increasing waste: Complex room shapes with many corners, cathedral or vaulted ceilings, intricate molding patterns, first-time installation. Each corner requires angled cuts - 4 corners = minimum 8 cuts = potential waste. Buy extra pieces rather than running short - matching dye lots later is difficult. Leftover pieces useful for future repairs.

Each corner requires two precise 45-degree cuts (or compound miters). Standard rectangular room: 4 inside corners = 8 cut ends. L-shaped room: 6 corners = 12 cuts. Each cut creates waste from test cuts and mistakes. Outside corners (bay windows, columns) more difficult than inside corners. Complex rooms with alcoves, beams, or architectural features need more material. Plan cuts carefully - long walls first, use scrap for short sections.

Materials vary by cost and use: MDF/Composite ($0.50-2/ft): Paintable, moisture-sensitive, easiest to cut. Wood ($2-8/ft): Pine, oak, maple - stainable, classic look. Polyurethane ($2-6/ft): Lightweight, pre-primed, moisture-resistant. Plaster ($5-15/ft): Traditional, heavy, ornate designs. Flexible molding ($3-8/ft): Curves and arches. Match material to room use - avoid MDF in bathrooms/kitchens.

DIY possible with right tools and patience. Required tools: Compound miter saw (essential for angled cuts), coping saw (for inside corners), nail gun or hammer, measuring tape, pencil, level, ladder/scaffolding. Skills needed: Accurate measuring, cutting compound miters (usually 33.9° bevel, 31.6° miter for 52/38 spring angle), coping inside corners, nailing into studs/ceiling joists. Practice cuts on scrap pieces first. Consider hiring pro for complex rooms or expensive materials.

Break irregular rooms into sections. Measure each wall individually and add them together. Bay windows: Measure each angled section separately. Curved walls: Measure with flexible tape or string, use flexible molding. Vaulted ceilings: Measure sloped sections along ceiling line. Tray ceilings: Calculate both levels separately. Account for transitions between sections. Sketch room layout with measurements before ordering. Add 20% waste for complex shapes.

Inside corners: Coping method (cut profile with coping saw) creates tighter joint than mitering, adjusts for out-of-square corners. Outside corners: 45-degree miters, both pieces meet at corner. Long walls: Scarf joints at 45-degree angle (not 90-degrees), locate over stud for nailing. Use wood glue on all joints. Fill nail holes and gaps with caulk. Sand smooth before painting. Quality joints more important than quantity of material - take time for precision cuts.