Choose a Quilt Size and Design First
You’ll need to make some decisions before you can calculate how much fabric is needed for a quilt:
Figure out how large the quilt will be, keeping standard mattress sizes in mind. Decide how much of the quilt top will be made up of quilt blocks, and how much of its size will be taken up by borders and/or sashing. Make a rough sketch on paper or use computer software to draw the quilt.
Other Considerations
What quilt block size will you use? How many blocks will it take across and down to fill the space within the quilt? For instance, for a quilt that measures about 60 inches x 80 inches, six 10 inch blocks across and eight 10 inch blocks down will fill the space, requiring 48 blocks. Be sure to add fabric for borders if you plan to use them, and decide if borders will be cut along the fabric’s straight grain or crosswise grain. Will blocks be straight set or placed on point? Multiply the block’s finished size by 1.41 to determine the width an on-point block will occupy in the quilt. Will you use plain setting triangles for on-point quilts? You can piece partial blocks to use as setting components, but if you don’t, you’ll need two types of triangles to fill in the jagged edges. Triangles look the same but are cut differently.
Decimal to Fraction Conversions
A conversion chart is handy for yardage calculations.
0.0625 = 1/160.125 = 1/80.1875 = 3/160.25 = 1/40.3125 = 5/160.333 = 1/3 yard0.375 = 3/80.4375 = 7/160.5 = 1/20.5625 = 9/160.625 = 5/80.666 = 2/30.6875 = 11/160.75 = 3/40.8125 = 13/160.875 = 7/80.9375 = 15/16
Analyze Quilt Blocks for Yardage Needs
Let’s say you want to make 20 identical Birds in the Air quilt blocks like the one shown in the upper right corner of the illustration. The blocks finish at 9 inches square. Look at the block’s grid. It’s a nine-patch design, with three major grids across and three down—nine units in all, even though the lower right block half is made from just one triangle. Keep in mind that the instructions below walk you through the layout of this particular quilt block—your blocks will differ. Sketch it out as you read, or print the image and follow along with the instructions.
Figure Yardage Requirements for Another Fabric
Now let’s figure the yardage requirement for the large green triangles. We’ll go through the steps a bit more quickly. Each large triangle is three grids high and three grids wide, making for a 9-inch square finished size. Add 7/8 inch to the finished size for seam allowances, for a cut size of 9-7/8 inches. Follow the same procedure for each part of the block, adding together yardages for like fabrics.
Quilt Border Yardages
Borders help you easily adjust the size of your quilt top. Vary the number of borders you sew to the quilt or adjust their widths to suit you. Once you’ve determined widths and styles, it’s easy to calculate border yardage. Keep in mind that mitered borders require longer strips than butted borders.
Sashing Yardage
Calculate yardage for sashing and cornerstones as you would for any other unit in the quilt. Make a rough sketch of the quilt layout to help you visualize how many strips are required.
