Easy Quilt Backing Calculator: Manual and Apps

Congrats, you have completed your exquisite quilt top, the next step is to select the perfect backing fabric.

With an abundance of options of fabric to complete your quilt back, opting for a 108″ wide backing can certainly simplify things when it comes to quilt backs.  

If you, however, can’t find 108″ fabric or you find the perfect 42″ wide fabric let’s talk about using a quilt backing calculator to determine how much fabric you need to finish your quilt. 

If you are looking to see what the different quilt sizes are you can download our quilt sizes chart.

Manual Quilt Backing Calculator Supplies

You can easily calculate how much quilt backing you need with some simple supplies you probably have at home. Grab the following supplies:

• Pencil
• Paper
• Calculator
• Your finished quilt top
• A measuring tape, quilters ruler or template

Manual Quilt Backing Calculator Steps

Step 1:

Take the measurements of both the length and width of the quilt top. I find it easier to lay out the quilt on a clean floor or my cutting mat depending on the size of your quilt. A rag quilt obviously takes up less space than a king-sized quilt. 

Step 2:

For machine-quilted quilts, it is advisable to add an additional 8 inches to both the length and width measurements. This includes 4 inches on each side and 4 inches on the top and bottom fabric pieces. This will help you know you have enough fabric to finish your backing.

Step 3:

To determine the required yardage, add together the length and width measurements, and then divide the total by 36. This will give you the amount of fabric needed in yards.

If your quilt is smaller than the width of the fabric for your backing, you have an easy task. You can simply cut the backing to match the length calculated in Step 2. 

However, if your quilt is wider than the fabric, you will need to determine the number of fabric widths required to piece together.

Multiply this number by the quilt backing length from Step 2 to obtain the total inches of fabric needed to purchase.

If your quilt exceeds approximately 42 inches in width, which is the standard width of a yard in a bolt of fabric, it’s important to consider that you will have a horizontal seam  or vertical seam in the backing fabric, unless you opt for 108-inch wide backing.

Step 4:

Cut the fabric to match the length of your backing and piece it together using 1/2″ seam allowances. Don’t forget to take into account any directional pieces and how you want your final back to look.

Tips and Tricks for Quilt Backing Calculator

Start by measuring your quilt top vertically and horizontally. Add 8 inches to both measurements to ensure you have an extra 4 inches all around.

This allowance accounts for fabric taken up during the quilting process and provides ample fabric for the quilting frame.

Trim off the selvages from the backing fabric and use a 1/2″ seam allowance when piecing it together. Sew the pieces along the longest edge and press the seam allowance open to reduce bulk.

For smaller quilts (under 60″ wide), use horizontal seams when joining the backing pieces. For larger quilts, opt for vertical seams.

If it helps with handling the quilt and conserving fabric, don’t hesitate to cut a length of fabric in half along the fold line. Note that larger quilts might require three lengths of fabric.

When selecting the backing layout, consider the pattern direction and pattern matching. Choose a layout that complements your quilt and enhances its overall beauty.

​Quilt Backing Calculator Example:

Let’s look at a pretend quilt and see how all the pieces come together when you are manually determining your backing fabric

After adding borders, the final dimensions of the quilt top are 58″ x 66″. To determine the required backing fabric size, add 8 inches to the quilt top width and length:

Quilt top width + 8″ = backing width

58″ + 8″ = 66″

Quilt top length + 8″ = backing length

66″ + 8″ = 74″

Next, calculate the number of Widths of Fabric (WOFs) needed for the backing by dividing the width measurement by 40″:

66″ divided by 40″ = 1.65

Round up to 2. You will need 2 WOFs for your backing.

Multiply the backing length measurement by the number of WOFs required:

74″ x 2 = 148″. This is the total inches of fabric needed.

Now, divide that number by 36″ to determine the yardage:

148 divided by 36″ = 4.1

Round up to the nearest ¼ yard, giving you 4 ¼ yards of fabric required.

Quilting Calculators Online and Apps

The Omni calculator allows you to input your width of fabric, length of the quilt and all the other dimensions and spits out how much yardage you need for your backing. 

If you love apps you will love the Robert Kauffman app. I have included a photo below so you can easily find it in your app store. It takes into account your quilt size, quilt’s width and more and tells you the amount of yardage you need for your quilt backing.

Using an app may help you use less fabric than determining the fabric needed for the back of your quilt manually. 

No matter what you use, it’s not difficult to determine the quilt backing you need no matter what size quilt you make. 

Don’t forget to join our quilt block of the month club, where you receive a free quilt block tutorial and can get the full quilt instructions to finish your quilt.