Crown Molding Calculator

1. Enter the room length and width in feet.
2. Set the number of inside corners (usually 4 for a rectangular room) and outside corners (0 for a simple rectangle).
3. Choose the stick length you plan to buy: 8, 12 or 16 ft.
4. Set a waste percentage (10% is standard for most rooms).
5. Enter the price per linear foot to see the cost, or leave it at 0.
6. Read the linear feet needed, pieces to buy, corner counts and estimated cost.

Crown molding is a decorative trim installed where walls meet the ceiling. It hides the joint, adds visual interest and can make a room feel taller or more finished.

Common materials include pine, MDF, polystyrene foam and polyurethane. Profiles range from simple cove shapes to ornate multi-piece designs. The molding is typically sold in 8-foot, 12-foot or 16-foot sticks.

Installing crown molding requires precise miter and cope cuts at corners, which is why a waste allowance of at least 10% is recommended. See the construction calculators hub for more building tools.

The calculator uses a straightforward perimeter-based approach with a waste factor and stick-count rounding.

1. Calculate the room perimeter from the length and width.
2. Add the waste percentage to get the total linear feet needed.
3. Divide by the stick length and round up to get the number of pieces.
4. Multiply pieces by stick length for the actual material you will buy.
5. Multiply the total with waste by the price per foot for the cost estimate.

Why Round Up?

Molding sticks come in fixed lengths. You cannot buy a partial stick, so the calculator always rounds up to the next whole piece. The leftover material helps cover cutting errors.

Take a room that is 14 ft long and 12 ft wide with 4 inside corners, 0 outside corners, 10% waste and $2.50 per linear foot. You plan to buy 8-ft sticks.

Perimeter: 2 x (14 + 12) = 52 ft.

With 10% waste: 52 x 1.10 = 57.2 linear ft of molding needed.

Pieces: 57.2 / 8 = 7.15, rounded up = 8 pieces of 8-ft molding.

Material to buy: 8 x 8 = 64 ft total.

Cost: 57.2 x $2.50 = $143.00.

You will have about 6.8 ft of extra material from those 8 sticks, which gives a comfortable margin for cutting errors at the 4 inside corners.

Crown molding comes in many widths and profiles. The most common residential sizes range from 2.5 inches to 6 inches wide.

Wider molding adds drama but costs more and creates more waste at corners. For most homes with 8-ft ceilings, a 3.5 to 4.5-inch profile is a good balance of impact and cost.

Every corner in a room where crown molding turns requires a precise cut. The type of cut depends on whether the corner bends inward or outward.

Inside Corners

An inside corner is where two walls form a concave angle, like the corners of a standard rectangular room. The preferred method is a cope cut: one piece is butted flat into the corner, and the joining piece is cut to follow the profile of the molding. Coping hides gaps better than mitering on inside corners.

Outside Corners

An outside corner is where a wall juts out, forming a convex angle. These are always cut with miter cuts at 45 degrees on each piece so the two pieces meet at a clean 90-degree joint. Outside corners are more visible, so tight joints matter.

Corner Count Guide

Measure at Ceiling Height

Rooms are not always perfectly rectangular. Measure along the ceiling line where the molding will sit, not at floor level.

Account for Irregular Walls

If a room has alcoves, bump-outs or bay windows, measure each wall segment separately and add them up.

Add Waste for Corners

Each corner cut wastes a small piece of molding. The 10% waste factor covers this for most rooms, but rooms with many corners or complex shapes may need 15%.

Buy from the Same Lot

Stain-grade molding can vary slightly between production runs. Buy all your sticks at once from the same lot for consistent color and profile.

Check for Obstructions

Mark the location of any vents, light fixtures or soffits that interrupt the molding run. You may need extra cuts and pieces around these.

Room Shape

A simple rectangle is easiest to estimate. L-shaped rooms, bay windows and alcoves add corners and short wall segments that increase waste.

Ceiling Height

Higher ceilings call for wider molding profiles, which cost more per foot and waste more at each cut.

Molding Material

Softwood and MDF cut cleanly and waste less. Hardwood and polyurethane are more brittle and may need extra material for test cuts.

Installer Experience

A beginner should add 15% waste instead of 10%. Coping inside corners takes practice, and early cuts often need to be redone.

Obstructions

Vents, light fixtures, soffits and cabinets that break the molding run create extra joints and extra scrap.

Before Buying Material

Run the calculator before you visit the store so you know exactly how many sticks to buy and what the cost will be.

Comparing Stick Lengths

Switch between 8, 12 and 16-ft sticks to see which option wastes the least material for your room.

Budgeting a Project

Enter the price per foot to get a quick material cost estimate. Compare MDF, pine and polyurethane by changing the price.

Planning Corner Cuts

The corner count helps you plan how many cope and miter cuts you need and whether to rent or buy a compound miter saw.

1. Skipping Waste

Every corner cut creates scrap. Buying exact perimeter footage almost always leaves you short.

2. Forgetting Outside Corners

Rooms with bump-outs or columns have outside corners that many people overlook when counting.

3. Measuring at Floor Level

Walls can be slightly out of square. Always measure at ceiling height where the molding will actually sit.

4. Not Buying from the Same Lot

Stain-grade molding can vary in color between production runs. Buy all your sticks at once.

5. Ignoring Profile Size

Wider profiles waste more at each miter cut. A 6-inch profile loses more material per corner than a 3-inch profile.

The math is exact for a rectangular room. Real rooms may need adjustments for non-standard shapes.

Measure the perimeter of the room and add 10% for waste. A 14 x 12 ft room has a 52-ft perimeter, so you need about 57.2 linear feet with 10% waste.

Divide the total linear feet (with waste) by the stick length and round up. For 57.2 ft with 8-ft sticks you need 8 pieces.

Use 10% for a simple rectangular room with 4 corners. Use 15% for rooms with many corners, complex shapes or if you are a beginner at cutting.

Inside corners are best done with a cope cut. One piece butts flat into the corner and the other is cut to match the molding profile. Coping hides gaps better than mitering.

Outside corners use miter cuts at 45 degrees on each piece so they meet at a clean 90-degree joint. Use a miter saw with the molding held upside down and at an angle.

For standard 8-ft ceilings, 3.5 to 4.5 inch molding works well. Taller ceilings (9 ft or more) can handle 5 to 6 inch or wider profiles.

Yes. Common lengths are 8, 12 and 16 feet. Longer sticks reduce the number of joints but are harder to handle and transport.

Prices range from about $1 per foot for MDF or polystyrene to $5 or more for hardwood or detailed polyurethane profiles.

Yes, but it requires compound miter cuts at angles other than 45 degrees. This calculator assumes flat ceilings with standard 90-degree corners.

No. Crown molding is decorative and optional. It is most common in living rooms, dining rooms and bedrooms. Bathrooms and closets often skip it.

• IRC (International Residential Code) -- Interior Wall Covering (Section R702 covers interior wall and ceiling finishes including trim installation requirements).
• This Old House -- How to Install Crown Molding (Practical guide covering measurement, cutting techniques and waste allowances for crown molding).
• Fine Homebuilding -- Crown Molding Installation Tips (Professional tips on inside and outside corner cuts, coping, and material estimation).