May 09, 2016
Have you ever seen the 'perfect' quilt block, only to discover that the directions are for a 12 inch appliqué block but, would you need to make it fit in a 10 inch square? If so, these simple formulas will help you with that 'higher' math!
OK, I admit to being a retired computer programmer, so am a bit of a geek. I also used to be an accountant, so it is reasonable that I like numbers and I like for them to "come out". Quilting just enables me to play with color and fiber and making it 'come out'.
Even before I was a programmer, hubby (who is also a programmer) would repeat the drill "Source - Target". When you copy files from one directory to another, you are always moving the files from the 'source' to the 'target'. Same thing applies with resizing a block for the copier, whether you want the block larger or smaller.
Beginning Block size
Preferred Block Size
Calculator
Copier Setting
Imagine a neat little appliqué that would be perfect for your wall, but the 12″block is too large. You want to make it a 10″square. You take the 12″pattern to a copier with the intent to make it smaller, but what percentage should you make it? In the words of my friend, “Ya start with whatcha want, and ya divide it by whatcha got.”
The copy machine wants a percentage, so move the decimal point to the right by two spots.
You need to reduce the 12″pattern by 83.3% to make a 10″block. Easy peasy!
You have an appliqué pattern for a 6″ x 7 1/2″ heart, and you decide you’d like to make it at least 8″wide. Ask yourself, what is it you want? An 8″wide block. What do you have? A 6″wide block. 8 ÷ 6 = 1.3333. Move the decimal point two places to the right, and got 133.3%.
How tall will it be? In this case you multiply the original height (7 1/2″) by 1.3333 (proportion number). So, 7.5 x 1.333 = 9.99975. The heart will be about 10″ tall.
One way to check that you did the math correctly is to remember the following. The proportion number will always be greater than 1.000 if you’re enlarging something, and will always be less than 0.999 if you want to make something smaller.
When changing the sizes of blocks, always do the proportion calculations with the numbers for finished sizes, not cut sizes. This is because you use different numbers to add seam allowances to a triangle (7/8″ for half-square triangles or 1.25″ for quarter-square triangles) than you add do for the seam allowances of a square or rectangle (1/2″). Do all the proportion calculations for the finished pieces first, and then add the seam allowances.