Spiros, I had a great question about enlarging a pattern from a customer today, and I thought you would find the information that I shared with her useful. 

Often when we think about increasing the size of a pattern — let’s say, to double, or 200% — we think we just have to double the yardage.  But that’s wrong. 

Since the design is increasing both in width and height we have to increase the yardage for both dimensions.  So, when you enlarge (or reduce) a pattern, you have to increase the yardage like this:

Yardage x % increase (width) x % increase (height) = new yardage

Let’s say you want to increase the size of a pattern 1-1/2 times, or 150%.  Your yardage calculations would be:

Yardage x 1.5 (width) x 1.5 (height) = new yardage. 

If you start with 1 yard, it works out like this:

1 yard x 1.5 (width) x 1.5 (height) = 2.25 yards.

If you wanted to make the pattern double its original size (200%), the yardage calculations would go like this:

1 yard x 2 (width) x 2 (height) = 4 yards