Hands holding white crown molding samples

Reference

Baseboard and crown molding sizes

Trim is named by one number — its height on the wall for baseboard, its width across the back for crown — and sold in a handful of sizes that have been standard for decades. Pick by the height of the ceiling, not by the profile in the store.

What is the standard baseboard size? Standard baseboard width (its height on the wall) is 3¼ in (83 mm), and the thickness is 9/16 in (14 mm) — the colonial profile builders have used for decades. Newer homes with 9 ft ceilings mostly use 5¼ in. Crown molding is most often 3⅝, 4⅝ or 5¼ in across the face, and most trim comes in 8, 12 and 16 ft lengths.

Standard baseboard sizes (floor molding sizes)

Baseboard — also sold as floor molding or base molding — is listed height first, then thickness. Thickness changes less than you would think — almost everything sold is between ½ and ¾ inch — but it decides whether the base sits proud of the door casing or awkwardly in front of it.

Height	Thickness	Thickness (mm)	Metric	Where you see it
2¼ in	7/16–½ in	11–13 mm	57 × 11–13 mm	Ranch and clamshell base in 1970s–80s houses
3¼ in	9/16 in	14 mm	83 × 14 mm	The builder standard. Colonial and ranch profiles
3½ in	½–9/16 in	13–14 mm	89 × 13–14 mm	Flat, square-edged modern base
4¼ in	9/16 in	14 mm	108 × 14 mm	A step up for 8 ft rooms
5¼ in	9/16–⅝ in	14–16 mm	133 × 14–16 mm	Today's standard in houses with 9 ft ceilings
7¼ in	9/16–¾ in	14–19 mm	184 × 14–19 mm	Tall rooms, older and period homes

These are the common baseboard sizes, and the standard baseboard dimensions you will find in any home center. Paint-grade MDF and primed finger-jointed pine come in all of these heights; solid oak and poplar are usually stocked only in the smaller ones.

Standard baseboard height by ceiling height

There is no code for it, only proportion. A designer's rule of thumb is about 7 % of the wall height, which on an 8 ft wall is 6¾ in. Treat it as the upper end: most rooms look right somewhat below it, which is where the table puts them.

Ceiling	Baseboard	Crown
8 ft	3¼ to 5¼ in	3⅝ to 4⅝ in
9 ft	5¼ in	4⅝ to 5¼ in
10 ft	5¼ to 7¼ in	5¼ to 7¼ in
12 ft and up	7¼ in or built up	7¼ in or built up

What size nails for baseboard?

The nail has to pass through the base and the drywall behind it and still bite about an inch into the stud. For a 9/16 in base over ½ in drywall that is 9/16 + ½ + 1 ≈ 2 inches, which is why 2 in finish nails are the default.

Trim	Nail	Into
Baseboard up to 9/16 in	15 or 16 gauge finish nail, 2 in Amazon	Studs and the bottom plate
Baseboard ⅝–¾ in, or over ⅝ in drywall	15 or 16 gauge, 2½ in Amazon	Studs and the bottom plate
Shoe molding and quarter round	18 gauge brad, 1¼ in Amazon	The baseboard — never the floor
Crown molding	15 or 16 gauge, 2–2½ in	Top plate, ceiling joists or blocking
Joining the miters	18 or 23 gauge, 1 in Amazon	Through the corner, with glue

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Shoe molding goes into the base rather than the floor so that a wood or laminate floor can still move underneath it. Nail baseboard in pairs — one low into the plate, one higher into the stud — at every stud, usually 16 in on center.

Crown molding sizes and dimensions

Crown is sold by the width across its back, but what you see in the room is how far it drops down the wall and reaches across the ceiling. Those two depend on the spring angle — the angle the crown's back makes with the wall. At 38° the crown stands upright and shows more on the wall; at 45° it splits the corner evenly. Most US crown is sprung at 38°, sold as "52/38".

Crown	Metric	Drop at 38°	Reach at 38°	Drop / reach at 45°
2¼ in	57 mm	1¾ in	1⅜ in	1⅝ in
3⅝ in	92 mm	2⅞ in	2¼ in	2⅝ in
4⅝ in	117 mm	3⅝ in	2⅞ in	3¼ in
5¼ in	133 mm	4⅛ in	3¼ in	3¾ in
6 in	152 mm	4¾ in	3¾ in	4¼ in
7¼ in	184 mm	5¾ in	4½ in	5⅛ in

Drop and reach are worked out from the face width and rounded to the nearest eighth, so a 4⅝ in crown at 38° lands about 3⅝ in down the wall and 2⅞ in out across the ceiling. Store names round these off: a "2 inch crown moulding" is really 2¼ in and usually sold as cove, a "6 inch crown molding" is anything from 5¼ to 6⅝ in across the face, and a "7 inch crown molding" is the 7¼ in size. Crown wider than 7¼ in is mostly built up from two pieces with a backer board.

Crown molding size for an 8 foot ceiling

3⅝ to 4⅝ inches. Anything wider starts to lower the ceiling visually, and an 8 ft room has little wall to spare above the door casing — the crown's drop and the top of the casing should not meet. At 9 ft go to 4⅝ or 5¼ in; at 10 ft, 5¼ in and up.

Shoe molding, quarter round and stock lengths

Molding	Size	Use
Shoe molding	½ × ¾ in	The smallest floor trim. Hides the expansion gap; slimmer than quarter round
Quarter round	¾ × ¾ in	The same job, rounder and bulkier
Door and window casing	2¼ to 3½ in	Usually about ⅛ in thicker than the baseboard, so the base butts into it

Home Depot and Lowe's stock trim in 8, 12 and 16 ft lengths; some yards add 10 ft, 14 ft is usually a special order, and door casing is often sold in 7 ft pieces cut for one leg. Longer sticks mean fewer joints on a long wall, and a joint on a painted wall is the first thing anyone notices. Add 10 % for miters on baseboard and 15 % on crown, where every outside corner eats a few inches.

The baseboard trim calculator turns a room into stock lengths of each molding, with the miter and bevel settings for crown.

Work out your trim →

Laying a new floor first? Laminate flooring thickness covers the expansion gap the shoe molding has to hide.

Figures: sizes as stocked by US home centers and lumber yards; profiles vary by mill, so the exact height and thickness are printed on the stick. Drop and reach calculated from the face width and spring angle.

Good to know

Questions, answered

Standard baseboard is 9/16 in thick (14 mm). Almost everything sold is between ½ and ¾ in, and the thickness is printed on the stick alongside its height.

The standard baseboard width, meaning its height up the wall, is 3¼ in (83 mm) in most US homes. Houses with 9 ft ceilings mostly use 5¼ in (133 mm).

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