Learn how to calculate sashing for a quilt using the easiest method there is! Learn what is sashing in quilting, how to add cornerstones, and how to calculate yardage for sashing.
There comes a time in every quilter’s life when they need to do some advanced quilt math and figure out how to calculate sashing for a quilt.
Especially with quilts that are using traditional blocks (or maybe not so traditional blocks), adding sashing is often that final piece of the puzzle that brings everything together.
I’m not going to lie, calculating sashing is one of the more complex calculations in quilting. But don’t worry. I’ll explain everything you need to know when planning sashing for a quilt. And of course – teach you how to calculate sashing for a quilt!
STOP STRESSING OVER QUILT CALCULATIONS
Let Quilt Geek do the quilt math for you!
What is Sashing on a Quilt
Before we go any further I want to make sure you understand what is sashing on a quilt.
Quite simply, sashing are the strips of fabric sewn between quilt blocks on a quilt top.
Sashing gives each individual block space to stand out, and adds negative space to the quilt.You might think it’s a very traditional design approach, but sashing can actually be a very powerful design element in modern quilts, as well.
How Wide Should Sashing Be On a Quilt
Before we learn how to calculate sashing for a quilt, we’ll need to decide on how wide we want the sashing to be.
The first and most important thing when deciding on sashing width is the difference between finished and unfinished sashing width.
The finished width of the sashing will always be less than the unfinished width of the sashing strips!
That’s because ½” will be ‘eaten up’ by seam allowance (¼” on each side of the strip).
So for example, if you want your sashing to be 3” wide finished (measured on the finished quilt top, after everything’s been sewn together) you need to cut strips from your fabric that are 3,5” wide.
Other than this technicality, there is no right or wrong way to determine how wide sashing should be on a quilt. If it looks how you want, then go for it. Nevertheless, here are two tips that you might find helpful if you need some direction.
Tip 1: Visually test out the width of sashing
Put your blocks (2 or possibly more) on a design wall or a large surface. Add a strip or two of fabric you want to use for sashing in between the blocks – make it wider than you think it will need to be. Then move the blocks to test out different widths of sashing strips.
When you’ve decided, you’ll just need to make sure you cut the auditioning strips to the width you decided on. Make sure you add ½’’ for seam allowance (¼” on each side).
Tip 2: Reflect a measurement in your quilt blocks
A great ‘safe’ way to decide on the sashing width is to repeat a measurement that’s already in your blocks. If, for example, your block is a 4×4 grid of 2” (finished) half-square triangles, you might want to choose 2” finished sashing strips.
We normally steer away from doing sashing that’s exactly half of the block width. But again, there are no rules, so whatever looks good for you will work!
What are Cornerstones on Sashing
If you want, you can also add cornerstones in quilt sashing. Cornerstones are small fabric squares or blocks that are placed at the intersections of the sashing strips. They serve both functional and decorative purposes:
Functionality: Cornerstones help to visually break up long runs of sashing. They can also make it easier to align the sashing and the quilt blocks.
Aesthetic Appeal: Cornerstones can add visual interest and variety to the quilt design. They can be made from a contrasting or complementary fabric, helping to tie the quilt’s overall color scheme together.
The size of the cornerstones is defined by the width of the sashing. If you’re making sashing that’s 3” wide when finished, your cornerstones will be 3×3” finished.
How to Calculate Sashing for a Quilt
Honestly, sashing can get a bit complicated to calculate and that’s one of the reasons we created Quilt Geek, our quilt calculator app.
I’ll first show you how to calculate sashing for a quilt with the app, and then I’ll explain how to do it by yourself.
We’ll use the following example to learn how to calculate yardage for quilt sashing:
Let’s say you want to add sashing to 9 of these pretty log cabin blocks.
The finished size of the blocks is 14×14”. You want three rows and three columns with 4” finished sashing strips.
IMPORTANT! FINISHED VS. UNFINISHED SIZE
14-inch FINISHED blocks refer to blocks that will measure 14×14” after they’ve been sewn in your quilt top. Before you sew them into the quilt top, the size of these blocks should be 14,5 “x 14,5 “ (the extra ½ inch will cover the seam allowance).
Similarly, 4” FINISHED sashing strips will be 4” wide after they’ve been sewn into the quilt top. Before sewing, they need to be 4,5” wide.
Option 1: Use the Quilt Geek Calculator
As you’ll see in a second, the Quilt Geek app’s sashing calculator is the quickest and easiest (and most accurate) option.
We offer a free trial, so you can work out the math you need for the project you’re working on with no charge at all!
Here’s how it works.
First, you’ll enter the dimensions of your blocks and the desired number of columns and rows for your quilt. You’ll also enter the width of fabric you’re using and the desired finished sashing width:
Now for the sashing layout. This is where Quilt Geek gets super exciting.
There are numerous options when planning sashing. You can go with just simple sashing strips. Or you can add sashing borders. And inner cornerstones. And outer cornerstones. Whew, that’s a lot of options!
Well, Quilt Geek will make these layouts super simple for you.
All you’ll need to do is choose the desired options:
SASHING BORDERS: YES or NO?
INNER CORNERSTONES: YES or NO?
OUTER CORNERSTONES: YES or NO?
As you click on the options, Quilt Geek gives you a diagram of your combo, so you can visualize it:
Let’s say you want:
- Borders
- Inner corner stones
- But no outer cornerstones
Choose the desired combo, and then click calculate and well – watch the magic happen.
Quilt Geek will give you all the quilt math instantly:
YOUR QUILT
- Number of blocks
- Finished quilt width and length
SASHING
- Total sashing length
- Width of WOF strips to cut
- Number of WOF strips to cut
- Total yardage
CORNERSTONES
- Total number of cornerstones
- Width of WOF strips to cut
- Number of WOF strips to cut
- Total yardage
You have to admit, this is pretty impressive. And just imagine how much time it will save you next time you’re planning a project!
(Not to mention money for all that extra-fabric-just-in-case!)
Quilt Geek’s handy Sashing Calculator calculates sashing, cornerstones, and sashing borders based on your desired sashing layout.
Learn more about Quilt Geek’s 20+ calculators and charts here or get started right away:
Option B: Calculate sashing for a quilt by yourself
I know I’m biased because Quilt Geek is our brainchild. But it’s just a fact that it is the easiest option. And again, with the free trial, you can calculate your project for free – even if you don’t decide to get the subscription afterward!
Nevertheless, I’ll show you how you can calculate sashing without the app.
I’ll show you the math for the most basic sashing layout, which is just sashing strips between the blocks. No borders, no cornerstones (see image below).
To calculate how much fabric you need, I recommend you make a little sketch and put all the dimensions down. Something like this.
Now the math. We’ll take it one step at a time.
STEP 1: Width of WOF strips
To get the width of WOF strips you need to cut, simply add 0.25” seam allowance on each side of the strip (0.5” total) to the desired finished width of sashing.
Width of WOF strips = 4” + 0.5” = 4.5”
STEP 2: The total length of sashing
Looking at the sketch, we can see that we need 2 long strips (50”) and 6 short sashing strips (14”). Each of these 8 strips will need to be sewn into the quilt top, which means we need some additional length for the seam allowance – that’s 0.5” for each of the 8 strips.
Total length of sashing = 2×50” + 6×14” + 8x 0.5” = 188”
STEP 3: Number of required WOF strips
We now need to figure out how many strips we need to make these sashing strips. Let’s say we’re using fabric with a WOF of 42”.
Keep in mind that you need to sew WOF strips together to get the long sashing strip. That’s why we’ll subtract 1’’ from the WOF (that’s got some room for error calculated into it). So the usable WOF is, in fact, 41”, assuming you’ll join the strips with a perpendicular seam (if you want to sew with a diagonal seam, you’ll need to subtract more).
Number of required WOF strips = 188” ÷ 41” = 4.58
→ rounded up that’s 5 WOF strips
STEP 4: Required yardage
Now that we know how many strips we need, here’s how to calculate yardage for quilt sashing:
Required yardage = number of required WOF strips x width of WOF strips
= 5 x 4.5” = 22.5”
You can convert that to yards, which would be exactly ⅝ yard.
(You should probably add some extra fabric for error.)
And that’s it. You’ve calculated how much fabric you need and how many strips you need to cut.
You can now make one looong strip using these 5 WOF strips. Then just cut the required length from this strip.
We don’t usually measure the length to cut. Instead, we lay the sashing strip next to the blocks or the row of blocks and cut as needed.
And if that sounds too complicated, start the Quilt Geek free trial and just do it there. It’s so much easier!
I hope I’ve shed some light on how to calculate sashing for a quilt. If you have any questions on how to calculate yardage for quilt sashing, just leave a comment below and we’ll try to help!
Happy sashing!
