Need Help With Math!
 

Hi all. Designing a small baby quilt for minky fabrics, which I've read should be sewn with 1/2" seam allowances.
I want each unfinished block to be 8" square.
For blocks with half square triangles, how do I determine what size to cut the fabric? Everything I'm finding online is for 1/4" seams of course.
Im also realizing my center of the 4 "f" block measurement will need tweaking, too, but I think I can figure that part out.
Thank you!!

Cut your P and G squares at 9-1/2" square.
Layer and sew 1/4" on EACH side of a diagonal line drawn thru the center of each pair of squares.
Cut on the drawn lines.
Press open.
Trim each square of HSTs to your required 8-1/2" size.

Jan in VA

The cutting size is correct, but I think that Jan had a typo on the seam allowance, she should have written: "Layer and sew 1/2" on EACH..." . We are so used to dealing with 1/4". For a quarter inch seam you would start with 8.5" squares, so the 9.5" will be a good size and will give you a bit of extra to trim. I would do a quick check and cut & sew 1 set to make sure it's what you are wanting.

Just to verify, you want your UNFINISHED size to be 8", making your finished size 7" if your are using 1/2" seam allowances. Is this accurate? From your drawing, it appears you want your FINISHED size to be 8".

I would add 1 and 1/2" to the finished size wanted to make the half square triangle blocks.

Cheryl7758, you are correct. I marked 8x8 on my pattern as cutting instructions to myself for the "F" blocks. The "F" is fox fabric, the "G" is gray and the "P" is pink.
I want each block to be 8" square before they are sewn together, except for the middle which will be a large square.
Thank you all for taking the time to help!

Paper Princess,
When you draw a line across the diagonal of the square, layer the square with another square right sides together, and sew....you WILL sew 1/4" away from each side of the drawn line. Then you cut ON the drawn line to separate the HSTs. :)

I may not have given her the corrct size squares to begin with as there now appears to be a debate about what the finished size actually is supposed to be.

Jan in VA

Jan, the way I read the original post was that she wanted the calculations for HSTs using half inch seams because she is not using quilting cotton. I'm thinking that cutting 9.5" squares per your post and sewing half inch seams should give her HSTs that could be trimmed to 8 &, with half inch seams, finish at 7.

Paper Princess is correct, I apologize if the markings on my drawing are confusing! I will start with 9.5" muslin squares to practice and see what I get! Thanks again!

Just be forewarned, that minky fabric is very STRETCHY!! I would NOT cut the triangles and try to sew the bias edge of minky.

Meaning don't do half square triangles at all using minky, or do it the technique described earlier with drawing the line and then sewing on each side of it? I'm planning to use a walking foot, pinning like crazy, and using a ball point needle (I think I have one!)