When one of my pattern testers had a similar issue with her center square-in-square block coming out a smidge too small, I decided to do a bit of investigation.
As a reminder, the math for the Square-in-Square block goes a little something like this:
Refresher - Square-in-Square Math ...
Measure one side of your center square. Let's say that it's 3.5".
- Divide this number by 1.4142.
- Add 3/8" (.375) for a seam allowance.
- Round the final number up to the nearest 1/8".
- Cut two squares using this measurement, and then cut each square in half, diagonally, to get your four outer triangles.
Let's walk through this using the actual numbers:
3.5 / 1.4142 = 2.4749
2.4749 + .375 = 2.8499
2.8499 rounded up to the nearest eighth - 2.875 or 2 7/8"
Cut 2 - 2 7/8" squares and then cut each in half diagonally.
Back to the Issue At Hand ...
I really take my pattern writing and accuracy very seriously. I want to give you the absolute best pattern I can. And while the math behind the blocks is sound - we've checked a dozen times and it's completely in line with the correct method of calculation - if you're still having difficulties with blocks coming out a tiny bit too small for what ever reason, try rounding your math up to the nearest quarter (or even half) inch and then squaring and trimming your blocks down to the pattern's required size.
Using the example above, rather than using 2 7/8" squares, try using 3" squares, or even 3 1/4" squares. Once the block is assembled, you'd trim the excess so that you're left with a 4 3/4" unfinished block.
I'll be adding a note to all the previous and future tutorials if you'll be using the "trim-down" method. Thanks so much for all of your feedback - I feel like I have the greatest readers!
Enjoy your three day weekend - we'll be posting block #6 Sunday afternoon ... in case you're looking for something to do on Monday's holiday. Happy sewing!!