Sample Yardage CalculationsLet's pretend we 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 will finish at 9" square.
Look at the block's grid. It's a nine-patch design, three major grids across and three down -- nine units in all, even though the lower right block half is made from just one triangle. (Read How to Analyze Patchwork for details about block structure.)
Keep in mind that the instructions below walk you through the layout of this particular quilt block, just for an example -- your blocks will differ. Sketch it out as you read, or print the image and follow along with the instructions. Analyzing quilt blocks becomes second nature once you've practiced a bit.
- Divide the finished size of the block, 9", by the number of rows across or down, 3. The answer, 3", is the finished size of each of the nine grids.
- All nine grids in this block contain half-square triangles, and we must add 7/8" to the finished size of a half-square triangle to calculate its cut size. (Read How to Cut Patchwork Shapes for details about patchwork seam allowances.)
- Each block has three dark blue 3-7/8" half-square triangles: we're making 20 blocks, so multiply that by 3 per block = 60 triangles. We can cut two triangles by dividing a 3-7/8" square once diagonally as shown.
- 60 triangles divided by the two each square yields = 30 squares required.
- Most quilting fabric has a usable width of about 40" (often a bit more). Divide 40" by 3-7/8", the size of your squares. The answer, 10.32, is the number of 3-7/8" cuts you can make across the width of the fabric. Slide that back to a whole number, 10 cuts. (See How to Cut Fabric Strips)
- Now divide 30 (the required number of squares) by 10 (the cuts you'll make per strip) = 3 strips required to cut the squares (assuming no waste).
- We're almost finished. Multiply 3 strips x 3-7/8" (the width of each strip) = 11-5/8" (total length of fabric required to cut 3 strips).
- A yard of fabric is 36" long, so divide the length of fabric required, 11-5/8", by 36". The answer is .32 yard (refer to the decimal conversions on page 1 if necessary). Bump up the yardage to compensate for errors or shrinkage during pre-wash. I would buy 1/2 yard.