Learn how to calculate quilt borders. Discover the perfect quilt border width formula and our step-by-step guide on calculating quilt border yardage.
Quilt borders can be an important part of your quilt part design. But the quilt math behind it can be a bit overwhelming, to say the least.
That’s why we’ll look into how to calculate quilt borders step by step. We’ll dive into what quilt borders are, and look at some tips on how to determinequilt border width.
Then we’ll explore two different methods for calculating border yardage you’ll need.
Let’s jump right in!
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What are Borders on a Quilt
Borders on a quilt are strips of fabric sewn to the outer edges that frame the central design or quilt top.
Borders can be added to the quilt sometimes for functional purposes – if you need a few more inches to the quilt and adding another row or column of blocks would be too much.
They can also be added purely for the visual effect. Adding a border frames the quilt top or the quilt blocks in the center of the quilt, making them stand out more.
There are endless options when it comes to designing quilt borders. You can add just one single border or multiple borders. The sky is the limit and the choice is entirely yours!
Quilt Border Width Formula
The first thing you need to determine to calculate yardage for borders is how wide to make quilt borders.
So how wide should a border be? How many borders to sew on a quilt? And do all borders on a quilt have to be the same size?
Let me put your mind at ease and remind you there are no hard rules in quilting.
Similar to sashing width, border width is completely up to you. And so is the decision of how many borders to put on a quilt, and whether they’ll be the same size.
The important thing to remember when calculating border yardage is that the width you need to cut fabric strips needs to be ½” larger than what you want your finished border to measure.
That’s because you need to sew the strips to the quilt top and ¼” will be eaten up on each side of the strip for seam allowance. (Even on the outer borders, ¼” is eaten up when attaching binding.)
Other than that, the choice of how wide should a border be is up to you. But if you want some help deciding, here are some tips.
Tip 1: Use the same width as sashing width
This is probably not so much a tip as it is an option. If your quilt has sashing, you can always make the borders the same width as sashing.
In fact, the sashing calculator in our quilting calculator app Quilt Geek gives you the option to automatically add quilt borders to the calculation. This means you can calculate sashing and borders (and cornerstones) in one go.
Tip 2: Visually test out the width of borders
A great hands-on approach to determine the quilt border width is auditioning different border widths on your finished quilt top.
Lay out your finished quilt top (or attach it onto a quilt design wall if you’re lucky enough to have one). Lay a strip of fabric along one (or more) side of the quilt and test out how it looks. You don’t need to cut all different possible widths, just move the auditioning strip underneath the quilt top to test out narrower strips and vice versa.
Tip 3: Use the golden ratio
A popular quilt border width formula when you want to add multiple broders is based on the golden ratio. The golden ratio is a ‘perfect ratio’ that makes things pleasant to the eye.
The golden ratio is 1:1.6 and if we use this idea for quilt border, it just means each border will be 1.6x the width of the previous border.
For example, if you want to make 3 borders and you decide the innermost border will be 2” wide, the following borders would be:
Border 1: 2”
Border 2: 2” x 1.6 = 3 ¼” (we’ve rounded up to the nearest ¼” because that’s easier to cut than 0.2”)
Border 3: 3 ¼” x 1.6 = 5 ¼” (again, rounded up to the nearest ¼”)
And so on.
Tip 4: Reflect a measurement in your quilt blocks
A great way to determine quilt border width is by using a measurement proportional to the geometry in the quilt blocks on your quilt.
For example, if your blocks are 9×9” Ohio star blocks you might want to use a quilt border that is 3” wide (one-third of the Ohio star block).
Mitered or Non-Mitered Borders
Aside from deciding how wide the borders should be, you’ll also have to determine if you want to make mitered or non-mitered borders.
Mitered borders are when the seam connecting the vertical and horizontal borders is at a 45-degree angle:
The difference between the two options is significant when you want to calculate yardage for quilt borders. Especially with wide borders, making mitered borders may require significantly more fabric. Which you of course need to calculate into your yardage requirements.
How to Calculate Quilt Borders
Now that we have all the basics covered, I’ll show you how to calculate quilt borders. We’ll pretend we have a 70×90” quilt top and want to add two borders:
- Border 1 will be 8 inches wide finished
- Border 2 will be 5 inches wide finished
IMPORTANT! FINISHED VS. UNFINISHED SIZE
Remember! When talking about finished sizes or widths, these are the dimensions AFTER the quilt top is sewn together. Unfinished dimensions (or widths) are always ½” wider for seam allowance.
Option 1: Use the Quilt Geek Calculator
I’ll start with what I genuinely and 100% believe is the easiest (and quickest and most accurate) option – with our quilting calculator app, Quilt Geek.
We offer a free trial, so you can work out the border math you need for the project you’re working on with no charge at all!
Here’s how to calculate quilt borders in Quilt Geek.
First, enter the following numbers in Quilt Geek:
- Border 1 finished width: 8”
- Border 2 finished width: 5”
(Quilt Geek lets you add up to 5 borders, so go border crazy if you want!)
Also enter:
Quilt width – which is the finished quilt top width (measured without borders): 70”
Quilt length – which is the finished quilt top length (measured without borders): 90”
Width of fabric (WOF) you’re using for borders.
Press CALCULATE and watch the magic happen.
Quilt Geek will instantly provide two calculations:
1 – MITERED CORNERS
2 – NON-MITERED CORNERS
For each of the two borders, it will tell you the width of WOF strips you need, the number of strips you need to cut, and total yardage required to make these borders.
Additionally, it will tell you how big your quilt will be after you’ve added all the specified borders.
You can even save the calculation for later and access it when you need – let’s say when you’re at the quilt shop picking up pretty fabric for your borders.
Quilt Geek’s handy Borders Calculator calculates everything you need to make up to 5 quilt borders!
It tells you how many WOF strips you need to cut and how much yardage you need – both for mitered and non-mitered corners!
Learn more about Quilt Geek’s 20+ calculators and charts here or get started right away:
Option B: Calculate quilt borders by yourself
Of course, you can always choose to skip the easy way and go straight to the more complicated, more time-consuming, and more frustrating way. Kidding, kidding, I’m not saying Quilt Geek is the only option (but it really is the easiest).
So I’ll show you how to calculate borders for your quilt by yourself, the old-school way.
We’ll use the same example as in the Quilt Geek calculation above.
We have a quilt that measures 70×90” (finished).
We want to add two borders:
- Border 1 finished width: 8”
- Border 2 finished width: 5”
I always recommend drawing a quick sketch to see what we’re dealing with – something like this:
Mitered borders take up more fabric than non-mitered, so we’ll go ahead and calculate for mitered borders. (The fabric will suffice for non-mitered borders, as well, but will leave you with some scraps.)
I’ll show you how to calculate Border 1 – the process is the same for all additional borders with one small change – I’ll explain that in a bit.
STEP 1: Width of WOF strips for Border 1
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 the border.
We want Border 1 to be 8” finished, therefore we need:
Width of WOF strips = 8” + 0.5” = 8.5”
STEP 2: The total length of Border 1
Looking at the sketch, we can see that we need two longer strips (along the length of the quilt) and two shorter strips (along the width of the quilt).
The length of the longer strips is:
Finished Quilt length + 2 x Finished border width = 90” + 2×8” = 116”
The length of the shorter strip is:
Finished Quilt width + 2 x Finish border width = 70” + 2×8” = 86”
For mitered corners, we add 4” for each mitered corner, that’s 16” total. This is for sewing the mitered corners together.
The total length of Border 1 is therefore:
2x 116” + 2×86” + 16” = 420”
STEP 3: Number of required WOF strips for Border 1
We now need to figure out how many strips we need to make these border 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 border 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 – Quilt Geek will do this for you automatically).
Number of required WOF strips = 420” ÷ 41” = 10.2
→ rounded up that’s 11 WOF strips
STEP 4: Required yardage for Border 1
Now that we know how many WOF strips we need, here’s how to calculate yardage for quilt borders:
Required yardage = number of required WOF strips x width of WOF strips
= 11 x 8.5” = 93.5”
You can convert that to yards, which would be 2 ⅝ yards.
(If you want, you can add some extra fabric for error.)
That’s it – for Border 1. For Border 2 (and any additional border you want to add) the process is exactly the same. The only difference is in Step 2.
Instead of using just Quilt width and Quilt length, you’ll use the width and length of the quilt top with Border 1 already attached.
This means you need to add 2x Border 1 width to Quilt Lenght and 2x Border 1 width to Quilt Width.
I know, I know, it sounds super complicated. And honestly, it can be. Which is exactly why we created Quilt Geek.
So again if you want the shortcut, start the free trial and calculate your borders with the app! You’ll be thanking us soon!
I hope I’ve managed to explain the complexity behind calculating borders for a quilt. If you have any questions on how to calculate yardage for quilt borders, let us know in the comments below.
