Could someone explain something to me, please?
 

I have been reading an article about organizing your stash and came across a line that said, basicallly- a finished square is 1/2 inch smaller than the original cut square. So if I have a 4 inch square, taken out of my red box, after sewing it to other squares, it should measure 3 1/2 inches - that is using 1/4 inch seam allowance. The accompanying illustration has the original square attached on all 4 sides.

****Why is the finished square only 3.5 inches and not 3 inches if you are sewing all 4 sides using a 1/4 inch seam allowance? After all, you are taking 1/4 inch off all 4 sides and 1/4+1/4+1/4+1/4=1***

I know math is not my strong suit, but am I that weak in it? :)

thank you so much! the things you think about when you have insomnia :p

Debbie

Because you only take 1/2inch from the length and 1/2 inch from the width.

Because you are only taking 1/4" off EACH of the 4 sides. left and right, top and bottom.

OH, I love this! This is indeed something that would keep me awake nights, too. It sure makes sense that 1/4 x 4 is 1. But when you split them up (1/4 on each side) it does boggle my mind, too. ......I hate math and always have-I usually call in help (DH).

Try it on a scrap of fabric and you'll get a visual of why it is true. You take 1/4" off the left, and 1/4" off the right, which adds up to 1/2" horizontally. Then you take 1/4" off the top and 1/4" off the bottom for a total of 1/2" vertically. So, your 4" square ends up being 3 1/2" at the end.

A similar case happened to me many years ago about the 7/8" added to a triangle.
I had to cut a square - say 6", then divide it diagonally into a triangle, then add the 1/4" all around and then measure the base to the tip of the diagonal line. It was 6 7/8". Then it all came clear to me.

This is the one I had to draw out for myself, too.

Yeah the 7/8 was confusing for me too. Once I drew it out i became clear.

This reminds me of my sister and I calculating measurements for an isolette cover. She's a nurse and I do accounting. We both calculate things in opposite ways. We just cracked up laughing while laying out our measurements...To hear us "arguing" over how to do it and both of us said this isn't rocket science!!

First, thank you for the responses... I'm coming to the conclusion this is something I just need "to do" and not think about. if I need a certain size finished square, I just need to cut the fabric 1/2 inch larger than I need for I am taking a 1/2 inch off the width and length. If I need 1/2 square triangles, I need to add 7/8"... (going to make a cheat sheet at home)...

but I just can't get my head around the reasoning (tell ya, I'm not good at math reasoning) if I taking a 1/4 inch off each side (1/2 " total for width and 1/2" total for length) that still gives me 1" taken off for seam allowances. why isn't that calculated- for 1/2 off width + 1/2 off length = 1").

ugh. guess there are some things I will never understand and that's why we have cheat sheets.... but now I know why my current quilt has gotten wonky...

thank you! :