In the previous post, I showed you how to make continuous bias binding.
The technique is great, but to really benefit of it, you should know how to calculate how much fabric you need to make the desired length of your binding.
I am glad to help you with this; I did the math for you, I made some cheat sheets and I also shared the formulas with you. You can download everything at the end of this post.
Calculate how much fabric you need to make a specific length of binding
If you know the length and width of the binding for your project, to find out how much fabric you need to make the desired amount, use this 2-step formula:
1. Length of binding x width of binding = ? (square inches needed)
2. Take the square root of the result above – this is the size of the square fabric you need.
Sqrt (length of binding x width of binding)=? (size of the square, round up to whole number).
Example:
length of binding: 55’’; width of binding: 2½’’
55 x 2.5 = 137.5
Sqrt(137.5)=11.72; round up to 12.
For a 55’’ length of binding, you need a 12’’ x 12’’ piece of fabric.
Replacing squares with rectangles
As you see, this formula gives a square fabric piece to work with. But what if you don’t have enough fabric for a square, and you have a rectangle instead?
You can replace the square with a rectangle. You just have to keep the same area of the fabric piece.
Here is an example:
The area of a 18’’ x 18’’ square piece of fabric is 18 x 18=324 square inches.
If you have a piece of fabric that is 42’’ wide, here is how to calculate the size of the rectangle:
324/42 = 7.714, so a 8’’ x 42’’ rectangle.
So a 18” x 18” piece of fabric produces the same length of binding as an 8” x 42” piece. I put the math to the test! See below!
- I received a message from a quilter who said that she does not understand how to make bias binding from a square piece of fabric. So check out the pictures below.
You have to cut the square diagonally.
Move the triangle as shown. This is where you could mess the thing! The new shape must be a parallelogram (bias edge parallel with bias edge and the straight cut edges parallel) – pay attention to this step and half of the job is done.
Next: you draw lines parallel with the bias edge – at the desired distance (the width of your binding). Stretch the edge to make sure it is the bias edge.
You will join the straight edges, so draw lines at 1/4” from the straight edges.
Here is how to offset the edges…
and how to pin the edges.
And here is the rectangular piece turned into a parallelogram,
and the straight edges you have to join.
If you do this for the first time, you may think it looks weird and can’t work, but I assure you: it works. Just match the points (don’t forget about the offset) and you will end up with a beautiful tube!
It looks like it is easier to join the edges of the squares than the edges of this extra long rectangle, but in reality it’s the same thing.
I measured the two bindings: 120” for the one made from the square fabric and 118” for the one made from the rectangular piece of fabric.
-
120” of binding (2 1/2” wide) achieved from a 18” x 18” piece of fabric; 118” of binding (2 1/2” wide) achieved from a 8” x 42” piece of fabric.
Calculate the length of binding you can cut from a specific fabric size
There is a two step formula for this, here is what you have to do:
Make sure your piece is a perfect rectangle (remove selvages, straighten edges…). Then measure this piece; you need to subtract ½’’ for seam allowances from both length and width of the piece.
You will calculate first the area of the piece and then divide it by the desired width of binding.
(length-0.5) x (width-0.5)= area of the fabric piece
area/width of binding = length of binding
Example 1:
24’’ x 24’’ piece of fabric; width of binding = 2½’’
23.5 x 23.5 = 552.25
552.25/2.5 = 220.9
A 24’’ square of fabric will yield 220.9’’ of binding, 2½’’ wide.
Example 2:
For a rectangle: 15’’ x 25’’; width of binding = 2¼’’
14.5 x 24.5 = 355.25
355.25/2.25= 157.88
A 15’’ x 25’’ piece of fabric will produce 157.88’’ of binding, 2¼’’ wide.
I hope this helps and the long explanation doesn’t make you think it is too hard to even try it! The cheat sheets will help for sure!
Happy quilting!
Very good tutorial. Thanks for sharing! Now I need to go and get some heavyweight threads 🙂
Thank you for the info on using a rectangle to make the bias binding! (Sometimes wish my brain was as creative as yours is!)
would it be possible to receive permission to reprint this in our guild newsletter for the rest of my quilting family to have access? or we can just give the link and they can look it up for themselves!~
Please share the link to my website, Bev. Maybe your friends will find other interesting ideas,too.
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Using the rectangle to make the bias binding. Oh my what a difference this makes. Thank you for laying out the process so, so well. I followed closely and had success the first time.
THANK YOU so much. I have a (supposed to be) quick pillow project for which I wanted to use piping in the seams. I have been stewing over the piping, not wanting to seam every strip individually. Your explanation with great illustrations was exactly what I needed to get this project done.
At last, the math behind continuous binding sizes! Such a relief from having to use charts that don’t meet all my needs. Now I can use math to figure out answers for myself. I thank you for this.
Love your clear pictures & explanation!
Still have problem getting enough binding out of a square.
Quilt perimeter=40″ x 40″.
40 x 4=160 (+15 extra inches)=175
175 (perimeter) x 3.25 (width of binding) =569
Sqrt of 569=24
This gave me enough binding for 3/4 of the quilt.
This happens every single time; the piece is never
long enough. Help!
I am finally getting some good info!! Spent the morning reading your website and printing your info so maybe I can start completing some projects!! Thanks so much!!