If I use 5" charms to make the 9P's, when the D9P block is cut and sewn back together, will it be 12.5" unfinished? I want to use up scraps, but I need a 12.5" unfinished block! SO not sure if I should use 4 1/2", 4 3/4", or 5" charms to make the block!

I can not believe you asked this question!!! My next project will be D9P and I've been wondering the exact same thing.

Thanks!

lol

now we just have to hope somebody has the right answer! :lol:

I havent tried this yet (on my to-do list) but if you just subtract a quarter inch for each seam in a side, that should give you the final size (did that make sense?)

I believe that would make it 14", or 13.5" finished. 4.75" would be 12.75"

You cut D9P twice - if you made a nine patch from 5" squares, your unfinished block would measure 14". You cut this again into quarters, yielding 4 blocks of 7" unfinished or 6 1/2" finished. I think of these as the final blocks and do my layout and join my rows using these quarter blocks but if you sewed four of them back together, you'd get a 13" finished block. If your original patches were 4 3/4", you'd get a 12 3/4" unfinished block by the above process. I'd do this then trim down, otherwise you'll be fiddling around with 1/8" :lol:

The formula is:
(size of patch x 3) subtract 1" ( 4 x 1/4" seams) = unfinished size of nine patch, then subtract 1/2" (represents 2 x 1/4" seams) = unfinished size of new block if nine patch is cut into quarters and sewn back together.

Reverse the formula to work back from your unfinished final block:

Unfinished final block + 1/2" + 1" divided by 3 = patch size so:

12.5" + 1/2" = 13" + 1" = 14" divided by 3 = 4.63", which is 4 5/8". :-D

NB - I made a mistake (see post below, this formula has been edited and is now CORRECT! - I hope! :lol: )

Wouldn't you get the finished size if you subtract 1 again after cutting for the second sewing? For the unfinished block you only need to substract 1/2 inch, as there are only two seem allowances per block direction.

You're absolutely right - I just went off to make coffee and it occurred to me that there was now one seam not two. So I came back to edit and saw your post. :lol: I'll edit mine above so as to not confuse anyone. :-D Although THIS post will then confuse them! Sorry, it's early morning here and my brain isn't up yet! :lol:

The easiest way to calculate the D9P is to add up the 3 unfinished size blocks and subtract 2" to get the finished size. I've got a couple right here that I'm working on and measured them.

4.5" unfinished x 3 = 13.5" (finishes to 11.5" )

5" unfinished x 3 = 15" (finishes to 13" )

The only ways to get 12.5" are to cut odd sizes, or use larger squares and cut down the whole block when you are done. If what you are making doesn't HAVE to be 12.5", why create a huge headache out of it, go a little smaller or larger! :)

I have a 1/4 block that i didn't use and it's measures 7 inches unfinished,so it would measure 13 inches with all 4.sewn together.Connie CO