Free crown molding calculator. Enter room dimensions and molding width to estimate linear feet, pieces and waste.
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Crown molding runs along the top of every wall at the ceiling line, so the material you need follows the room perimeter rather than the floor area. This crown molding estimator takes your room length and width, or a direct total wall length for L-shaped rooms, then adds your chosen waste percentage to cover the angled off-cuts at every corner. It divides the waste-adjusted total by your molding stick length and rounds up to whole pieces, because molding is only sold in full sticks, and it prints a corner-cut guide from your inside and outside corner counts.
The perimeter formula is the heart of this estimate. It has three steps. First, the room perimeter: for a rectangular room, perimeter = 2 × (length + width). A 14 ft by 12 ft room has a perimeter of 52 ft. Second, the waste allowance: multiply the perimeter by (1 + waste / 100). With a 12 percent waste allowance, 52 ft becomes 52 × 1.12 = 58.24 ft of molding. Third, the pieces to buy: divide the waste-adjusted total by the stick length and round up to the next whole piece, because lumber yards sell molding in full sticks only. 58.24 ft divided by 8 ft sticks = 7.28, rounded up to 8 pieces. Rounding up is never wrong here: the leftover from the 8 sticks covers future repairs. Unlike baseboard, no deduction is made for doorways, because crown molding sits at the ceiling line well above standard doorway height and runs continuously across them.
Measure each wall corner to corner at the ceiling line, since that is where the crown molding will sit. Write every measurement on a simple sketch of the room, labeling walls A, B, C and so on, so you do not mix them up. Measure to the nearest 1/16 inch and measure each wall twice to catch mistakes. If the room is L-shaped or irregular, switch the calculator to the total wall length mode and enter the sum of all wall segments instead of a length and width. For vaulted or sloped ceilings, run the tape along the actual ceiling slope, not horizontally, and plan for extra waste since the angled cuts are more complex. A laser measure speeds up long runs, but keep it level and steady.
Crown molding sits tilted between the wall and ceiling, a position defined by its spring angle. Most manufactured crown uses a 38-degree spring angle (written 38/52), while larger profiles often use 45 degrees. Because the molding is tilted, corners need compound cuts: a miter setting and a bevel setting used together. For a standard 90-degree inside corner with 38/52 spring-angle crown, set the miter saw to 31.6 degrees miter and 33.9 degrees bevel. For outside corners the miter direction reverses but the angles stay the same. For 45-degree spring-angle crown, the standard settings are 35.3 miter and 30 bevel. Many professional installers cope inside corners instead of mitering: one piece runs square into the wall and the next is cut to overlap its profile. Coped joints are more forgiving of walls that are not perfectly square and do not open up as walls settle, which is why pros prefer them. Coping does not change the amount of molding to buy.
A waste allowance of 10 to 15% is the standard recommendation for crown molding, slightly higher than for baseboard because every corner needs a precise angled or coped cut and beginners make more installation mistakes. Choose 10% for a simple rectangular room with an experienced installer, 12 to 15% for most DIY projects, and 15 to 20% for rooms with many inside and outside corners, angled walls, or vaulted ceilings. The waste covers the off-cuts from mitered corners, short returns over windows, test cuts, and the occasional miscut. One subtlety: the percentage rule works well for typical rooms, but if your walls are much longer than your stick length, plan the actual pieces onto sticks instead of relying on the percentage, because each joint consumes real material.
Crown molding comes in fixed sticks, commonly 8, 12 and 16 feet long. Longer sticks mean fewer joints on long walls, and joints at inside corners are far less visible than joints on a prominent straight wall, so plan your piece layout with that in mind. Ceiling height does not change how much molding you need, since the estimate is based on the floor plan perimeter; however, taller ceilings usually call for a wider, more elaborate molding profile, which affects cost per linear foot rather than length. Molding width therefore does not change your linear-foot estimate, only your budget. If cost matters, enter a price per foot with a supplier and multiply by your waste-adjusted total. Finally, do not skip measuring: crown molding projects fail when the estimate is guessed, and an accurate perimeter plus a generous waste allowance is what keeps you from making a second trip to the store.
Measure the room perimeter, 2 × (length + width) for a rectangular room, or add up all wall lengths for an irregular room. Add a 10 to 15% waste allowance, divide by the stick length, and round up to whole pieces. This calculator does all of that for you.
Every inside and outside corner is cut at an angle, which wastes a few inches per joint. Short returns over windows and the occasional miscut add more loss. A 10 to 15% allowance covers those losses plus a safety buffer so you do not run short mid-project.
No. Crown molding is installed at the ceiling line, well above standard doorway height, so it runs continuously across the top of doorway openings with no deduction.
No. The estimate is based purely on the room's floor-plan perimeter, which is the same regardless of ceiling height; it does not affect the total length. Taller ceilings may call for a wider profile, which affects cost per foot, not total length.
Yes. Coped joints, where one piece runs square to the wall and the next is cut to overlap its profile, are preferred by many professional installers because they are more forgiving of out-of-square walls and do not open up as walls settle. Coping does not change how much molding you need to buy.
Measure every wall that will carry molding and add the lengths together to get the true perimeter, then use the calculator's total wall length mode. The waste percentage, stick length rounding and corner guide work the same as for a rectangular room.
Yes. Crown molding is sold in full sticks, so you always round up to the next whole piece. The leftover material is useful for repairs later, which is why the calculator rounds up automatically.
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