Calculate how much crown molding you need from room size, wall lengths, or perimeter, including cutting waste, sticks to buy, and material cost.
Crown Molding Length Formula
L = P * (1 + W/100)
P = 2*(RL + RW)
N = ceil(L / S)
- L is the total crown molding length to buy (ft or m)
- P is the ceiling perimeter (ft or m)
- W is the cutting waste percentage (%)
- RL and RW are the room length and width (ft or m)
- N is the number of sticks to buy, rounded up
- S is the length of one stick as sold (ft or m)
The calculator finds the ceiling perimeter in one of three ways. If you enter a room length and width, it uses the rectangle formula P = 2*(RL + RW). If your room is not a simple rectangle, you can enter each wall length individually and the calculator sums them. If you already know the perimeter, you can enter it directly. In every mode the perimeter is multiplied by the waste factor to get the total length to buy, and that length is divided by the stick length and rounded up to get the number of pieces. The advanced options add a material cost estimate from a price per stick or per foot, count the angled corner cuts you will make from your inside and outside corner counts, and recommend a crown size in proportion to your ceiling height.
Recommended Crown Size by Ceiling Height
Buying the right length is only half the decision. Crown that is too small looks lost on a tall wall, and oversized crown crowds a low ceiling. The ranges below reflect common design practice for single-piece crown.
| Ceiling height | Crown height range | Notes |
|---|---|---|
| 8 ft | 3 to 5-3/4 in | Stay near the low end in small rooms |
| 9 ft | 4-1/4 to 7 in | The most flexible height for standard profiles |
| 10 ft | 5 to 8 in | Larger profiles read as intentional, not bulky |
| 11 ft and up | 8 in or larger | Consider a built-up, multi-piece crown |
Typical material prices help turn your length result into a budget. Prices below are per linear foot for material only, not installation.
| Material | Typical price per linear foot | Best for |
|---|---|---|
| MDF | $1 to $4 | Painted crown on a budget |
| Pine and softwood | $2 to $6 | Paint or light stain, easy to cut |
| Polyurethane foam | $2 to $6 | Moisture-prone rooms, lightweight installs |
| Hardwood (oak, maple) | $5 to $15 | Stain-grade, high-end finish work |
Example Problems
Example 1: A rectangular living room measures 16 ft by 12 ft, and crown is sold in 8 ft sticks. The perimeter is P = 2*(16 + 12) = 56 ft. With the recommended 15% waste factor, L = 56 * 1.15 = 64.4 ft. The number of sticks is N = ceil(64.4 / 8) = 9, so you would buy 9 sticks, or 72 ft of material.
Example 2: An L-shaped kitchen has six walls measuring 14, 10, 6, 4, 8, and 14 ft. The perimeter is the sum, 56 ft. The room has an extra corner pair, so you choose 20% waste: L = 56 * 1.20 = 67.2 ft. Using 16 ft sticks, N = ceil(67.2 / 16) = 5 sticks, which gives 80 ft purchased and about 12.8 ft of spare material for miss-cuts on the compound miters.
Crown Molding Length FAQ
Do you subtract doors and windows when measuring for crown molding? No. Crown molding runs along the joint between the wall and ceiling, so it passes unbroken above door and window openings. Measure the full length of every wall at ceiling level and use the total. This is the opposite of baseboard, where you do subtract door openings.
Why buy longer sticks than the calculator's minimum? Every joint in the middle of a wall is a scarf joint that must be cut, glued, and sanded, and it can open up as the wood moves seasonally. If a wall is 14 ft and you only have 8 ft sticks, you are forced to joint mid-wall. Buying 16 ft sticks lets each wall be a single piece, which looks better and installs faster, even if it slightly increases leftover material.
What waste percentage should you use? Use 10% for a simple four-corner room if you are comfortable with a miter saw, 15% as the standard allowance, and 20% or more for rooms with many corners, bay windows, or if this is your first crown installation. Inside corners consume material because each coped or mitered end needs extra length to cut, and a single miss-cut on an 8 ft stick can scrap the whole piece.
