Monday, September 24, 2012

Because I'm Me-Jelly Roll Quilt Math

Because I am who I am I figured out how to figure out how many strips and how wide to make the strips for a particular size quilt. This is an excel spreadsheet and if you want to make one  yourself  you could do this as well. The yellow boxes are the numbers you enter. You could set it up just as I have by entering the formulas in the cells I've pointed out. For example: in cell A3 type (without the quotes) "=(A2-0.5)*32". Because you sew and cut 5 times the length of the quilt is always 32 strips. You can vary the length by changing the width of the strip.

To figure out how wide the quilt will be, work backwards. Each time you sew and cut the width doubles, so if I want a quilt for a queen size bed, and I want it to be 80 x 100 I first entered 2 1/2 as the strip width but that only gave me a length of 64 (the finished width of a 2 1/2 inch strip is 2 inches). I then put in 3 inches and got 80 inches for my length.

For the length I decided I wanted 100 inches, when I enter that into the third yellow box, the number doubles to 3200 inches. When I divide that by the length of strips I have (44 inches) I get a result of 72.7 strips. I would make that 73 strips and cut off a bit.

If you want to use the spreadsheet I made to try it out, it's here.

The chart below is just for reference. Have fun.


Allie said...

Oh my gosh Mary this makes my head hurt - lol - I'll stick with applique!!!!

Teri said...

Thanks for the math. I also worked backwards. I figured it for a queen bed by making 2 quilts and sewing them together. The whole doubling thing is where it gets tricky.

Beeshebags said...

I've also been calculating out how to alter the sizing (I make quilts for Aussie Hero Quilts which are 42" wide x 72" long, so the JRR quilts are a bit short and too wide, but with a little math, and alot of sore heads, my friend and I calculated out the method (still got to do a final trial though) and something I worked out is after you've sewn the first three times, you just simply add a row of random strips on one end....this will then alter the quilt to end up at 36 rows or 72".

Alas, the closest we could get the width to, was 43.36" but at least this way you don't have to trim too much once it's quilted (I prefer to Stitch over the ditch using a fancy zig zag stitch!) so you don't lose length :o)

Hope I've made sense.



Related Posts Plugin for WordPress, Blogger...