How to Size Crown Moulding: Projection, Height, and Length

Three numbers on a Spectis crown plate tell you if the stick fits: projection, height, and length. This guide explains each one, gives a starting size for your ceiling or eave, and lists the sizing mistakes we see most often. It is written for homeowners, builders, and architects ordering crown for interior rooms or exterior cornice.

Projection, height, and length

Projection is how far the crown stands off the wall. A deep eave needs more projection than a bedroom ceiling. Height is how far it drops down the wall. On an 8-foot ceiling, about 3 to 5 inches of height is the usual start, and a taller wall takes a taller profile. Length is the stick. Most Spectis crowns are 12-foot sticks. A few decorative profiles are closer to 139 inches. Order the waste.

Dentil, two-step, boxed, and fossil-stone crowns are separate filters. The plate, not the photo, is the size.

What size crown to order

Crown fails when it is too small for the wall or too deep for the soffit. Height is the vertical face. Projection is how far it comes off the wall. Both numbers are on the cut sheet for that profile.

Confirm the cut-sheet height against the actual wall. These ranges are a start, not a substitute for the plate.

Crown sizing tips

Match the crown to the room. An 8-foot ceiling with a 7-inch crown looks top-heavy unless the room is wide or the ceiling is trayed. A 12-foot foyer with a 3-inch cove looks unfinished.

Size exterior cornice to the eave. Exterior cornice is sized to the eave, not to the room inside. If the overhang is 12 inches, do not order a 16-inch projection and hope.

Use the spring angle for that profile. Spring angle is profile-specific. The compound miter on a 38-degree crown is not the setting for every Spectis stick. Use the angle on that SKU’s cut sheet, or cope the inside corners if your saw work is stronger that way.

Count build-ups as one crown. A crown cap over flat stock over dentil can be the right size even when no single stick matches the chart. Read crown cap, crown with flat stock, and 2 step crown before you invent a stack from loose lumber.

Order length from the perimeter. Order from the actual perimeter plus waste for miters, not from a room’s longest wall. A 12-foot stick does not finish a 12-foot wall once both ends are mitered.

Ready to choose a profile? Browse Spectis crown moulding, then see how to install Spectis crown moulding and cornice.