Monday, 2 November 2015

Quit Maths - Triangles

Not everyone likes doing math and from time to time there can be a lot of it involved in making a quilt.  Anyone who has ever made a Triangle quilt and seen how much it shrinks in width when pieced, will appreciate the effort  Yvonne @ Quilting Jet Girl has gone to, to make a calculator specifically for equilateral triangles.  Check out Yvonne's post today and bookmark her page 'cause the next time you are making a triangle quilt this will come in handy!

You can download the spreadsheet and save it for a later date if you wish - thank you Yvonne for this!

Equilateral triangles are those where the internal angles are all 60 degrees and the three sides are all the same length.  Trigonometry gives equations for working out height when you know length and vice versa. When designing quilts these equations can be used to determine the width of your finished quilt and the number of triangles you need to cut.  After making a quilt that turned out smaller than expected I worked out an equation and kept in on hand in OneNote but Yvonnes spreadsheet now makes this so much easier!  And there are options for adding pieces to square your quilt or cut away at the ends.

During the Triangle- A-Long hosted by the Sassy Quilter we made 6" triangles cut from strips and it gave me a 58" quilt.  This turned out a lot smaller than I wanted but I wanted to keep my colouring and not change my design by adding more triangles.   What I could have done was made my triangles bigger.
I find it easiest  now when working with triangles to determine the height first as it is a really simple calculation in comparison to the width.  For equilateral triangles  the rule of thumb is to add 3/4" to the desired finished height of your triangle.  A 6" cut triangle gave me a 5 1/4" height per row and approximately 58" tall quilt.

Changing to 7" triangles would have given me almost a 69" quilt and a more usable width of nearly 58".
Yvonne's spreadsheet makes it so easy to play around with these figures and end up with a quilt the size you need!  I am hoping to use some of my Halloween fabric for a pointy triangle quilt next year and will definitely be coming back to this calculator again!


  1. You explain it all so wonderfully, Ruth! It really is easy math to figure out the height of a triangle quilt, and remembering 3/4" instead of 1/2" for shrinkage is the trick. The width is a bit more fiddly, and I really hope my tool and different finishing options are helpful for the community. Thanks so much for sharing about it today!

  2. It would have made my life so much easier at the time had I this available to play with. Very generous to allow us to download it for future use too - thanks a million!

  3. Not knowing the finished size worked fine when I was making a scrappy triangle quilt (just add more scraps), but if I ever wanted a neat planned finish like your colourwash, something like Yvonne's calculator would be a sanity saver.


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