16 Patch Double Pinwheel Project – How to figure out the 16 patch size

Hi Everyone…me again,

I’ve been working diligently on this project and now that all of the Double Pinwheel Blocks have been re-sewn back together I want to make an equal amount of 16 Patch Blocks to use as an alternate block for this quilt.

The problem that has come up now, is how do I figure out what size to make each of the little squares in order to have the finished block be the same size as the trimmed down Double Pinwheel? Have you ever tried designing your own pattern or do you just use the directions someone else creates for you?

For this project I HAVE to come up with my own measurements. This will be a good learning lesson though as it will be the first time I have a specific size square that needs to be broken up into 16 equal pieces! Middle school math I keep telling myself! Any 12 year old should be able to figure it out!

So here goes.I have trimmed each of the pinwheels to 4″ square. Four of those blocks get sewn together for the Double Pinwheel Block. That block works out to be 7 1/2 inches square. Therefore, my 16 patch needs to end up being 7 1/2 inches square as well.

To figure this out I need to know what the block size is SEWN into the quilt and divide one side length of the block into 4 equal lengths, and then add back a seam allowance. Easy peasy.

So if the square is now 7 1/2 inches that would make it 7 inch square once a 1/4 inch seam allowance is used. So now, divide 7 into 4 equal pieces. If I divide it into 2 equal pieces, half of 7 is 3 1/2. Then half of 3 1/2 is 1 3/4! So each of the 16 patches is 1 1/4 inches square once sewn!

Add back a 1/4 inch seam allowance to each side and that comes to 2 1/4 inches square. Whew!!!!I know at this point, now that I’ve figured out the dimension, I can do either a strip piecing technique or cut the scraps into squares and put together 4 patches. Most likely I’ll try both techniques in the making of these blocks but for now, I’m trying to use up some scrap muslin, which there’s not too many scraps long enough for strips so squares it is! We’ll see how many blocks I can get out of the scrap and then if I need to do more I’ll work out a strip piecing system.

Here’s the 16 patches. A little note to myself as these first few have been turning out slightly smaller than the 7 1/2″ square. I’m having to steam press them into shape, not ideal, but working so far. I just have to remember that the more seems there are in a block the more accuracy of seam allowance and exact cutting really counts!!