Psst: It’s really all about what looks good to you and how big you have to make the quilt.
Like other areas of quilting, there are some mathematical formulas to assist in determining border size:
1) Golden Ratio: Finished size of most commonly used block x 1.618 or .618 = finished border width
2) Rule of thumb: 1/2 to 2/3 the largest block in your quilt
3) Fibonacci numbers: 0, 1, 1, 2, 3, 5, 8, 13, etc. (helpful for determining proportions for multiple borders)
For example, in the memory quilt I’m currently making, my blocks are 15″ finished with 2″ finished sashing and contrasting cornerstones between the blocks. I was going to add my standard 5″ finished outer border, but it didn’t look right – it didn’t look big enough. Nor did it even come close enough to the 72″ length the customer preferred.
So, out comes my trusty calculator:
Using the Golden Ration, my finished border should be: 9.25″ [This actually put the quilt at 71″x71″]
Using Rule of Thumb, my finished border should be 7.5″ to 10″
Using a different Rule of Thumb, my border should be 1/3 of the finished block or 5″
Scratch #3 – even with the 2″ sashed inner border, it’s still too small.
So, I booted up EQ7 and plugged in the numbers to see what was the most visually appealing
Golden ratio was most visually pleasing, but I didn’t have enough fabric to do that, so I cut 8.5″ wide strips instead.
If short of fabric, I could’ve used the Fibonacci numbers to determine the sizes of the pieced borders – 3″ and 5″ to make that 8″ border I wanted. The quilt will finish about 70″ square with binding, so I think we’re good.