OK ladies, I'm fairly new to the quilting world and I am really stumped when trying to figure out what size blocks to cut to frame the center of my quilt top when not using a purchased pattern. Say my center is 36x36 and I want to use 2, 3 or 4inch half square triangles. How do you figure that out. Is there a chart I can download? Cause figuring all the seam allowance makes my head spin. :cry:

Ok some may disagree with me.
If it were me I would cut squares of two different colors or prints the same size. Enough to go around your center piece. Make sure you make the same mount of both. Now lay them right sides together, draw a line diagonally down the middle and sew 1/4 inch on either side of that line. Now cut them apart on the middle line and press open. You should have two triangles sewn together into a square. The bias is on the seam line so they should not stretch a lot. use the squares to make your border. It doesn't really matter what size they are as long as they are all the same they should come out a consistant size. I think it is traditional to pick the size block you want finished and add 7/8 of an inch to that measurement when cutting the blocks. The only problem I have with that is that precise a measurement always gets me in trouble. I tend to stick with whole numbers and trim down if necessary.
I also find that adding an inch or even two border between the center and the border of triangles is more interesting, helps the quilt grow and is easier on the eye. A little wider plain border after the triangle border usually looks good .

OK. I was wondering how to figure out how many triangle blocks (whatever size I chose) to line up exactly with the edges of my quilt center.
I'm not very good at explaining this. Example ..If I needed to make a border of 3" blocks to equal 36". what size blocks do I cut, figuring in the seam allowances?

if you're quilt measure 36 inches and you want to figure out what sizes you could use - i would go with any number that divides into 36 equally.

36/2 inches = 18 blocks
36/3 = 12
36/4 = 9
36/5 = no good, its not a whole number
36/6 = 6 blocks
36/8 = no good, its not a whole number

so, you get the idea. now you should decide what size block will look good with the style of the quilt. that really just comes down to what you like and the look your going for.

the cuts you have to make to achieve the correct finished size is 7/8 larger for triangles and 1/2 larger for straight cuts - this accounts for the seam allowances.

Just adding that you also need to add 4 corner blocks in your calculations , in additon to the sides, top and bottom.

It's a good example of why odd sizes don't always work out right. Sometimes it is easier to add a border in order to bring the hst layer into easier calculations.

Thank you so much! That is what I needed to know. I figured it had to be something simpler than what was going on in my brain! I can see now that this forum is going to be a wealth of information. You're all the best.

thank you moonpi, i would have felt terrible when she posted that she doesn't have any corners :shock:

Suggestion:

maybe make two or threetest HST squares and then join them together to make sure they are coming out to the expected size before you cut out a lot of them.

I find that cutting the squares plus one inch and trimming the excess works out better for me. The plus 7/8 ones end up skimpy for me.

And you will find MANY suggestions for how to make HSTs here.

I do a lot of trials because I kind of make a lot of errors.

So - that's why I have all suggestions for making samples -