I am definitely a "visual" person. I do, however, add more than 7/8" when cutting squares to make 1/2 square triangles - I like being able to trim them to the correct size. I like knowing they will be exactly the size I want them to be and being able to trim them allows me that. I have had to "tug" on too many to make them fit - I guess that means I need to do a better job at sewing an accurate stitching line, but it is easier to trim them afterwards.