How to use it
- Pick a material preset (sewing, EVA foam, sheet metal, cladding or paper), then the units.
- Choose the shape and enter its size. For a ball you can enter the circumference you measured with a tape instead of the diameter. For a dome, enter how wide it is across the opening (the span) and how high it rises.
- Enter the number of gores. More gores make a rounder shape with narrower pieces.
- For thick foam or metal, say whether your size is to the outside or inside and enter the thickness. Add a seam allowance (sewing) or an overlap on one edge (cladding), a top disc to avoid a bulky point, or a straight wall under a dome.
- Download the PDF and print it at 100% / Actual size (measure the rulers first), or the DXF/SVGfor a cutting machine. Every setting is in the page address, so you can share the exact pattern.
How the gore shape is worked out
Each gore is drawn the standard way: a straight centreline, with the width set off square to it. At a distance s from the top, measured along the curve of a sphere of radius R, the gore is as wide as that slice of the sphere's circumference divided by the number of gores N:
width = 2π · R · sin(s / R) / N
So the widest point, at the equator, is the circumference divided by N, and a full gore is half the circumference long. A crown disc of diameter d simply starts the gores where the sphere is d across, and the N gore tops then add up to the disc's circumference.
Worked example: a 160 mm half sphere in 12 gores. Each gore is 125.7 mm long (π × 160 ÷ 4) and 41.9 mm wide at the base (π × 160 ÷ 12). Measured from the base, the width is 41.9 mm at 0 mm.
Many layout videos draw each side of a gore as a single compass arc. That is close for domes but leaves the panels slightly too full, which is why a scaled-up pattern can look like a pumpkin. The curve here is the exact one, sampled every quarter of a degree.
Not sure how many gores to use, or how to get a dome's radius from its span and rise? See how to make a sphere or dome pattern.
Fabric, foam and metal
- Fabric: the pattern line is the stitch line. The seam allowance is added outside it at a constant width (it is never enlarged with the pattern), and it is cut square at a point so all the gores meet at the pole. With many gores, a small top disc avoids a bulky point.
- EVA foam and other thick material: the pattern is drawn on the middle of the thickness, so a ball measured to the outside comes out the right size. The width table gives the edge bevel: half the angle between neighbouring gores, largest at the equator (22.5° for 8 gores).
- Sheet metal (orange-peel domes): use the mean diameter (outside − thickness), often with a crown disc. For insulation cladding, measure over the insulation and add the overlap on one edge.
Examples to start from
- A 160 mm half sphere in 12 gores, with the width every 10 mm
- A newborn hat from a 37.7 cm head measurement, in 4 pieces
- A 78 in giant ball with 44 in wide fabric
- A 35 cm EVA foam sphere in 10 mm foam
- A dome 8 in across and 4 in high, in 12 pieces
Limitations
- Gores make a sphere out of flat pieces, so the finished shape is slightly faceted; fabric and foam ease into the round, metal needs forming. More gores reduce the facets.
- Stretchy fabric and heat-formed foam change size. Make a test piece from scrap before cutting good material.
- This is a layout aid. It does not design pressure vessels, parachutes or load-bearing structures: for those, follow the relevant design rules and standards.
Frequently asked questions
- How many panels should a fabric ball have?
- Six is the classic plush ball; 8 to 12 look rounder. With fewer than 6 the ball looks lumpy.
- I only know the circumference. Is that enough?
- Yes. Choose "Circumference" and enter it; the tool works out the diameter.
- Do I add the seam allowance myself?
- No. Enter it and the PDF, DXF and SVG include it, with the stitch line marked inside the cut line.
- Is anything I enter sent to a server?
- No. The pattern and the files are made in your browser. Your settings are kept in the page address so you can share them; see privacy for what the host and analytics receive.