I have an 8.5 block and I want to cut two contrasting materials and place them back to back and sew down the center to make a triangle on each side but I want it to come out to an 8 size block. what size should the two contrasting colors be.

Can someone help. I am new at quilting but want all the blocks to be 8 inches some solids and some with contrasting color.

Your help is so appreciated.
Quiltbaby
Tennessee

Hope you get an answer, I am too visual to understand what you are exactly asking.

The RULE is add 7/8" to the size you want, draw a diagonal line corner to corner, stitch 1/4" on each side of line then cut on line.
It is a tad easier to just add 1 " , mark, sew and cut then square up. You will only take a little sliver off --but-- it will be square. No actual waste just more accuracy. This is how I do it, but to each her own.
Have fun. Ruth

I'm not good at that stuff either. My solution would be to cut the 2 squares 10", sew the center seam, press, open out and cut it to the size you want. Seems like a lot of work but that is the way I do things when I don't have a set pattern. You could also do this with paper first, rather than wasting fabric.

Cabinqltr has the answer. I always go to the next inch and then square the blocks after making the HST. I just find it easier to cut at even inch and it allows for a little more forgiveness on your diagonal seams.

thank thanks so much. I am going the next inch and square the block. I just could not think of that. Thank all of you for your expertise. I know I love this site and I am happy to be a learner here.

Have a great day.

Quiltbaby
Tennessee

8 7/8" exact but you have to be sure your seam is totally accurate or it will come out too small. Best to go with 9" cut squares and then square down to your 8.5.
Make a test block first to test your cutting and seam allowances. your fabric, thread, needle size etc can all effect the finished size. So best to cut larger and then recut. Less frustration that way.

I am a visual person and as they say a right brain person. I have to keep asking questions until I get and visualize. Many times I can understand a simple answer instead of a complex on. There is nothing at all wrong with being visual. That too is a gift.

Have a great day.

Thanks everyone for all of your answers.

I won't even admit to the way I read this at first. I wasn't thinking half square triangles. I think I need more sleep.