Sample Yardage Calculations
Let'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.)
- 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: 20 blocks x 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 2 per square = 30 squares required.
- Most quilting fabric has a usable width of about 40" (often a bit more). Divide 40" by 3-7/8". The answer, 10.32, is the number of 3-7/8" cuts you can make across the strip. Slide that back to a whole number, or 10 cuts. (See How to Cut Fabric Strips)
- Now divide 30 (required squares) by 10 (cuts per strip) = 3 strips required to cut the squares (assuming no waste).
- We're almost finished. Multiply 3 strips x 3-7/8" (width of each) = 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). Bump up the yardage to compensate for errors or shrinkage during the pre-wash. I would buy 1/2 yard.
