Fabric Calculator


Unit of Measurement
A. Radius (?)
One half of the umbrella's fabric diameter -- measure over a rib from one edge to the center point.
B. Number of Gores (?)
The number of triangular pie shaped panels with seams radiating from the center (often 8 as in the image above and never less than 3).
3 to 20
Hem (?)
Finished width of the doubled hem all round the Umbrella. A one inch hem would add two inches of fabric to the length of each gore. This will be zero if a binding is used to finish the circumference of the umbrella.
C. Open Diameter (?)
Measure the diameter of the opened umbrella if possible. This diameter will normally be roughly 10% less than twice the radius measured above. This measurement determines the shape of the umbrella "cone".
Fabric Width (?)
Actual width of fabric (often 46, 54, or 60 inches -- 1168, 1372, and 1524 mm)
Vent with Fly:
A 16 inch opening will be provided at the center with a 28 inch circular fly to cover it.
There will be no hole at the umbrella's center.