How much fabric you need for a round table cloth will depend on the width of the fabric you are using; the pattern on the fabric, if any; and your chosen method of hemming the cloth. To prevent shrinkage of the finished cloth, the fabric should be laundered in the same way it will be cleaned after construction.
Choosing The Fabric
These cloths are best suited to light to medium weight woven fabrics such as as quilters cotton, broadcloth, percale, bridal satins and drapery fabrics. Flat bedsheets are a good option. Knit fabrics are not suitable because of their stretch. Very tightly woven fabric such as canvas and heavy weight fabrics such as upholstery will not drape.
Fabric Calculation Using Wide Fabric or a King Flat Sheet
To the width of the finished cloth add 1 inch, which allows a 1/2 inch hem all around. This is the length and width of the piece of fabric necessary to make the cloth. If the fabric you have chosen is this wide you will need 91 inches of fabric, or 2 5/8 yards. (91 divided by 36 inches per yard)
Fabric Calculation Using 45-inch wide fabric
Most quilters cottons are 45inches wide. To join pieces together to make a 91-inch wide piece of cloth you will require: 91 divided by 45 equals just over two pieces. Always round up, therefore you will need three, pieces of 45 inch fabric, 91 inches long. This equates to 7 5/8 yards. (91 times 3 equals 273 divided by 36 inches per yard)
Fabric calculation using 54 inch wide fabric
If the required fabric piece is 91-inch wide and long and your fabric is 54-inch wide, you will need two pieces of fabric, joined together and cut to the 91 inches round. (91 divided by 54 equals 1.7; round up to two) Two pieces of fabric 91 inches long equates to 5 1/8 yards. (91 times 2 equals 182 divided by 36 inches per yard)
Natural fibers may shrink in washing; therefore purchase at least 15 percent extra fabric or purchase a swatch and launder it to determine actual shrinkage. The seller of the fabric may be able to tell you how much the fabric will shrink. Blends of man-made and natural fibers, such as polyester and cotton, will shrink less than natural fibers, but some shrinkage may still occur.
If the chosen fabric has a pattern that will require matching when being seamed extra fabric will be required. To calculate this: determine the size from the top to the bottom of the pattern. Divide the 91 inches required by this measurement and round up. As an example: the pattern repeat is 9 inches. Divide 91 by 9 to equal 10.1, round this up to 11. Multiply this number by the pattern repeat number (11 times 9) to equal the new length of each piece of fabric which is 99 inches or 2 3/4 yards per length of fabric to be joined no matter what the width.