Pinwheel Quilt: Calculate your Fabric Amounts

As you may know, there are three parts (not including batting) to each quilt: quilt top, quilt backing, and quilt binding fabric. Below is a detailed explanation of how I calculate yardage needs for the pinwheel quilt (as well as general calculation methods I use for all quilts). I know it’s not thrilling reading, but if you want to make a quilt for yourself, and you don’t have a pattern, this information may be helpful to you.

Quilt top:
As you can see from the drawing I created here, there are 105 pinwheel blocks and 184 white blocks. Here’s how I calculated my fabric needs for each of these.

Pinwheel blocks: I’ll discuss how to make pinwheel blocks in a future post, but I start with one 5″ square block of pink, and one 5″ square block of pink to make one 5.5″ pinwheel block. We need 105 of each of these 5″ square blocks to make 105 pinwheel blocks.

  1. Determine how many squares you can cut from one strip of full width (42″ not
    including the selvage) fabric.
    42″ width / 5″ = 8.4 or 8 squares per strip (We round this number down, because anything less than one fabric square is considered a scrap).
  2. Divide the total number of squares needed by the number of squares that each strip yields.
    105 squares needed / 8 squares per strip = 13.125 strips or ~ 14 strips (We round this number up because each strip needs to be 5″ wide in order to get a full square.)
  3. Multiply the number of strips by the width of each strip to get the total number of inches of fabric. Then, divide that number by 36 to get your yardage. Always round up.
    14 strips * 5″ wide strips = 70 inches
    70 inches / 36 inches per yard = 1.94 yards or ~2 yards.

Result: We need two yards pink and two yards white to make our pinwheel blocks.

***Alternatively, if available, you can buy charm packs of fabric, which are precut packages of 5″ square fabrics. This will save you considerable cutting time, but the downside is that you may or may not be able to purchase charm packs in your choice of color. Similarly, charm packs usually come in amounts from 21 to 42 squares per pack, which may mean you have to buy extra. I wasn’t able to buy charm packs  for the colors I chose, but I always love a shortcut!

White blocks: To make our white filler blocks (non-pinwheel blocks), we go through the same steps as above, EXCEPT for these blocks, we need 184 5.5″ squares.

  1. 42″ width / 5.5″ = 7.63 or 7 squares per strip.
  2. 184 squares needed / 7 squares per strip = 26.3 strips or ~27 strips
  3. 27 strips * 5.5″ = 148.5 inches
    148.5 inches / 36 inches per yard = 4.125 yards  or ~ 4.5 yards.

Backing fabric:
Whether you have your quilt professionally quilted, or your quilt it yourself by machine or by hand, your backing needs to be bigger than your top by 4 – 6″ all the way around. Since our quilt is 85″ x 85″, the backing needs to be about 96″ x 96″. You can piece your backing with regular 44″ fabric, or you can buy wide fabrics. I have done both, and certainly, the wide fabrics make things easier, but your choices for colors and prints can be limited. You can also piece your back vertically or horizontally, depending on your preference. Piecing a back horizontally is sometimes good, because it can require less fabric for a quilt that is longer than it is wide. However, if your fabric is directional, you may need to piece it vertically. For this quilt, it’s a square, so there is no advantage to piecing it one way vs. the other, unless your fabric width is 60″. In each of the fabric width scenarios below, I’m assuming a length of 96″, which is 2.66 yards. I round this up to 2.75 yards. 44″ fabric width requires 3 pieces (2.75 yards * 3 = 8.25, for example).

Here’s a chart to help you decide:

Fabric Width Pieced Vertically Pieced Horizontally
44″ wide fabric 8.25 yards 8.25 yards
60″ wide fabric 5.5 yards 3.5 yards
108″ wide fabric 2.75 yards 2.75 yards

Always remove your selvages before piecing your backing fabric!

For the binding, I always use a 2.5″ width, so I will base my calculations on this. You may need to make adjustments based on your preferences.

  1. Calculate the perimeter of your quilt.
    (Length of quilt * 2) + (Width of quilt * 2) + 44″ (extra) = (85 *2) + (85 * 2) + 44″ = 384″
  2. Divide the perimeter by the width of the fabric (44″) to determine the number of strips you will need.
    384″ inches around quilt / 44″ strips = 8.7 strips or ~9 strips.
  3. Multiply the number of strips by 2.5″ to get inches and divide by 36″ to get yardage.
    9 strips * 2.5″ = 18.5 inches. This is about a half a yard, but I will round up to 2/3 yard to make sure we have enough.


Pink Fabric White Fabric Other Fabric
Pinwheel Blocks 2 yards 2 yards
White Blocks N/A 4.5 yards
Binding 2/3 yard N/A
Backing N/A N/A 2.75 – 8.25 yards
Totals 2.66 yards 6.5 yards depends on fabric width


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