Understanding your result
The headline is the sheets of board for the curve, with the layers and faces under it. A curved wall is usually two thin layers, so the sheet count is twice what the area suggests, and if both faces of a free-standing curve are boarded it doubles again. The tiles give the board area, the number of studs along the arc, the screws and the compound.
The first note is the bending check. It compares your radius with the published minimum for the method on the face you chose and says whether the board will make the bend dry, whether it needs wetting, or whether the method is wrong for the radius. A convex (outside) face is always harder than a concave one for the same radius, and the limits in the table reflect that.
The table shows the arc length from the radius and angle, the face area, the sheets per layer per face with waste, the studs at the close spacing the curve needs, the screws per layer and the tape and compound for the face layer. The framing side of the job is in the wall stud calculator for the straight returns on either side; the straight walls themselves go through the single wall calculator, and the thickness selector is where the “which board here?” question is answered for the rest of the house.
How we calculate this
The minimum radii come from two public sources: the Gypsum Association’s figures for standard board bent dry with the long edges perpendicular to framing at 6 in on centre (1/4 in: 5 ft; 3/8 in: 7 ft 6 in; 1/2 in: 10 ft), and National Gypsum’s published table for its 1/4 in flexible board (dry: 32 in concave, 30 in convex at 9 in on centre; wetted: 20 in and 14 in at 6 to 9 in). Other makers’ flexible boards are close but not identical; use the data sheet of the board you buy. The waste default is 20% because a curve is cut at both ends of every sheet and the offcuts rarely fit the next curve; the waste factor calculator explains the choice.
Screws are counted at 16 in along each stud, the Gypsum Association’s wall spacing, through every layer; the close stud spacing makes the count high. Compound and tape are for the exposed face only, at the Level 4 figure from the coverage table.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Standard board minimum radius, dry | 1/4 in 5 ft; 3/8 in 7 ft 6 in; 1/2 in 10 ft; 5/8 in 15 ft | Gypsum Association (GA-216 curved-surface provisions), long edges perpendicular to framing at 6 in on centre |
| Flexible 1/4 in board, dry | 32 in concave, 30 in convex; framing 9 in on centre | National Gypsum High Flex technical data (at 65 °F and 45% humidity) |
| Flexible 1/4 in board, wetted | 20 in concave, 14 in convex; framing 6 to 9 in | National Gypsum High Flex technical data |
| Layers | Two for 1/4 in and 3/8 in methods, one for 1/2 in | Standard practice (USG, National Gypsum installation guides) |
| Stud spacing on the curve | 6 in (standard board), 9 in (flexible, dry), 6 in (flexible, wetted) | The spacing published with each radius |
| Screw spacing | 16 in along each stud, every layer | Gypsum Association GA-216 wall spacing |
| Waste | 20% | Our figure for curved cuts; see the sheet sizes table for sheet areas |
Assumptions last reviewed October 8, 2026.
The calculator does not design the framing of the curve (plates cut from plywood or kerfed lumber, or curved steel track) and does not count corner bead for the vertical edges where the curve meets a straight wall, which take flexible bead or paper-faced bead. Cold, dry conditions reduce how far any board will bend, and the published figures were measured in a warm, moderately humid room. The thickness and board type guide covers 1/4 in and flexible board among the others; the sheet orientation guide explains why bending direction matters.
Two worked examples
A half-circle bay of 4 ft radius, 9 ft tall, flexible board
Concave face only, two layers of 1/4 in flexible board dry, 4 × 8 sheets, 20% waste.
- Arc: 4 × π × 180 ÷ 180 = 12.6 ft; face area 12.6 × 9 = 113 sq ft
- Bending check: 4 ft radius against a 32 in (2.7 ft) minimum for flexible board on a concave face: fine, dry
- Sheets per layer: 113 ÷ 32 × 1.2 = 4.24, rounded up to 5; two layers: 10 sheets
- Studs: 151 in ÷ 9 in + 1 = 17; screws 17 × 7 per stud × 2 layers = 238
- 1.1 gallons of compound, one pail; 60 ft of joints on the face layer
With standard 1/4 in board the 4 ft radius would fail the check (5 ft minimum) and the calculator would say so; flexible board makes it an ordinary job.
A gentle 20 ft curve of 12 ft radius, boarded both sides, single 1/2 in
Length mode, 20 ft along the arc, 8 ft tall, both faces, one layer of 1/2 in board.
- Face area: 20 × 8 = 160 sq ft per face
- Bending check: 12 ft radius against the 10 ft minimum for 1/2 in board dry: fine
- Sheets: 160 ÷ 32 × 1.2 = 6 per face; two faces: 12 sheets of 1/2 in, 320 sq ft
- Studs: 240 in ÷ 6 in + 1 = 41; screws 41 × 7 × 2 faces = 574
- 3 gallons of compound, one pail
A 12 ft radius is a gentle sweep, the kind a curved kitchen island wall or a stair wall has, and a single layer of 1/2 in makes it with 6 in studs. At 9 ft radius the check fails and the wall goes to two layers of 1/4 in.
Where to find your inputs
Radius. From the plans, or by measuring: for a circular bay, the distance from the centre of the circle to the wall face. If you only have the chord (the straight line between the ends of the curve) and the depth of the curve, the radius is (chord² ÷ (8 × depth)) + depth ÷ 2.
Angle. 90° for a quarter circle, 180° for a half; a typical curved corner is 90°. Use the length mode instead if you can measure along the curve with a tape pressed to the framing.
Face. Concave is the inside of the curve (you are standing inside the circle), convex the outside. A free-standing curved partition has both.
Method. Two layers of 1/4 in standard board for radii of 5 ft and up, flexible board below that, wetted flexible board for the tightest curves, and a single 1/2 in only for 10 ft radii and gentler.
Common mistakes
- Framing at 16 in. Board bent between studs 16 in apart flattens into facets. Six to nine inches, as the method requires.
- One layer of 1/2 in on a tight curve. It cracks at 8 ft radius and below. Two layers of 1/4 in.
- Bending across the width. Standard board bends lengthwise; the published radii assume the long edge runs perpendicular to the studs.
- Wetting the face paper. Wet the back, let it soak, bend, screw, and leave it to dry on the wall before taping.
- Cold-weather bending. Below about 60 °F the board is brittle. Warm the room and the board first.
- Standard corner bead on the edges. The vertical edges of a curve meeting a flat wall take flexible or paper-faced bead, not rigid metal.
Questions people ask
- What is the minimum radius for bending drywall?
- Dry, with the long edges perpendicular to framing no more than 6 in on centre, the Gypsum Association's figures are 5 ft for 1/4 in board, 7 ft 6 in for 3/8 in, 10 ft for 1/2 in and 15 ft for 5/8 in. Flexible 1/4 in board goes to about 32 in on a concave face and 30 in convex dry, and to 20 in and 14 in wetted, per National Gypsum's High Flex data.
- How many layers of drywall on a curved wall?
- Two layers of 1/4 in board, standard or flexible, is the usual build: each layer bends easily and the two together are as stiff and as thick as one 1/2 in sheet. A single layer of 1/2 in board works only on gentle curves of 10 ft radius or more. The joints of the second layer are staggered from the first and only the face layer is taped.
- How close should the studs be on a curved wall?
- Closer than a straight wall: 6 in on centre for standard board bent to its minimum radius, and 6 to 9 in for flexible board depending on the radius and whether it is wetted. A 90° curve of 6 ft radius is 9.4 ft of arc, which is 19 studs at 6 in rather than 8 at 16 in. The plates are cut or kerfed to the curve.
- Do I need to wet drywall to bend it?
- Only for radii tighter than the dry limits. Wetting the back paper with 10 to 15 oz of water per side and letting it soak 10 to 15 minutes lets flexible 1/4 in board reach a 14 in convex radius; the sheet is bent in place, screwed, and left to dry on the framing for a day before taping. Wet bending of standard board is possible but less predictable.
- How many sheets for a curved wall?
- Length along the curve times height gives the face area; multiply by the layers and divide by the sheet area, with 20% waste because every sheet is cut to the arc. A half-circle of 4 ft radius 9 ft tall is 12.6 ft of arc and 113 sq ft per layer, which is 5 sheets of 4 × 8 per layer, 10 sheets for two layers of flexible board.
- Horizontal or vertical sheets on a curve?
- Horizontal, with the long edge perpendicular to the studs, for standard board: that is the direction the minimum radii are published for, and it bends more easily lengthwise. Flexible board is published both ways, lengthwise with the easier radius. Vertical sheets on a curve put the stiff direction across the bend.