"Calculating Half-Square Triangles"
Many quilters tend to go into a "flat-spin" the minute you mention anything to do with formulas and mathematics. And although working with triangles can be tricky, there
are a few "simple secrets" that will
take out all the stress of calculating these measurements.
Some patterns do provide you with
the measurements for quick-piecing
half- square triangles but many only
give the starting triangle size. Unfortunately, this limits you to the "slowest" and least accurate piecing method.
And for those who are designing and creating their own quilts, you'll want to know the "quick and easy" way to calculate the measurements to quick-piece your half-square triangles.
So, how do you determine the proper cutting dimensions for quick-pieced, half-square triangle units?
It's easy -- here's how...
CALCULATING THE CUTTING SIZE FOR QUICK-PIECED HALF-SQUARE TRIANGLES
The calculations are based on the finished size of the blocks. So, your first step is to determine your finished block size. Then you add the "magic number" to this and you're done!
The "magic number" for half-square triangles is 7/8". You simply add 7/8" to the required FINISHED SIZE of your half-square triangle unit.
So, for example, if you want a 4" (finished size) half-square triangle unit, you need to cut two squares that measure 4 and 7/8" each. For a 5 and 1/2" (finished size) half-square triangle unit, you need to cut squares that measure 6 and 3/8". Quite easy really!
You place them together and prepare the half-square triangle units as shown in the quick-pieced half-square triangle instructions.
Remember: Cut your squares 7/8" larger than the finished size of the half-square triangle unit to make these units using the quick-piecing half-square triangle technique.
HOWEVER... very often you will find that the squares are
still slightly small.
You can try sewing the squares together with seams that are slightly less than 1/4" from the marked center line. But I prefer to cut the squares "larger" and then trim them back, if necessary. It adds an extra step,
but I believe it is well worth it.
My philosophy --it's always easier to cut a little off but you can never add a little on.
So -- I always add 1" to my squares, instead of the recommended 7/8".
After the units are sewn and pressed, align them "squarely" under a rotary ruler with a diagonal line, ensuring the diagonal line matches with your seam line. Then, trim them back to the exact finished size that you require.
This is especially helpful when using "grid-pieced" methods as you don't have to measure out odd sizes like 4 and 7/8"! It is also ideal if you are making miniature quilts, because a tiny difference has a BIG impact on little blocks.
So -- there you have it. The "quickest and easiest" methods for calculating and piecing half-square triangle units!
I wish you the best of luck with your next "half-square triangle" project!
I hope you've found these instructions for "calculating half-square triangles" useful.
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