Need help with measurements please
 

Hope someone can help me because I feel very math challenged right now.
If I was to make a rail fence quilt sewing 5 strips, 2 1/2" each together, what width would I cut it to make a square block?
I was thinking 10" but not sure and would like someone to explain please.

You would cut the blocks 10.5" when sewn together they finish at 10". This will allow for seam allowances.

10.5" --- You will lose 1/2" between each strip for seams... 1/4" from each strip side

This will give you a 10" FINISHED BLOCK

Press your sewn strip sets and measure the height. Then cut your blocks to the same width.

I do same as quiltRfun. As Mary Ellen Hopkins said, "It's your measurement."

I usually think of the finished size of a strip and then add up the number of strips. I do a lot of quilt design on EQ7 so you have to when drawing think of the finished size. Sew the strips together, press and cut the same length as the final width of your strip. Doesn't matter on a Rail Fence if you blcoks are a little bit short or long.

I agree with the others---after sewing the 5 strips together, press and measure the width. Cross cut the same size to get a square. If your seams were accurate, it would be 10 1/2".

Thanks to all.