Downsize or Upsize?

A friend at the guild meeting the other night asked me about changing the size of a quilt pattern or re-sizing a quilt block to fit your needs.  Little did she know that this is something I love to do.  I thought I would share a little about it here.
When re-sizing a quilt block pattern, one of the most common mistakes is disregarding the seam allowance.  In quilting, the seam allowance is almost always a quarter inch, and you have to remember that it is a quarter inch on both sides of the cut piece.  So the first thing you need to do when re-sizing a pattern, either making it smaller or larger, is to "remove" that seam allowance before doing the math.  1/4 inch on one side plus 1/4 inch on the other side equals 1/2 inch, so you need to remove 1/2 inch from the measurement before re-sizing.  For example, if the pattern says to cut a 2 1/2 inch strip, and you want to half-size the pattern or make it half as big, then you need to "remove" 1/2 inch seam allowance from the 2 1/2 inch measurement.  You are now left with 2 inches, you then divide THAT measurement in half, which equals one inch and now you have to add that seam allowance back in - leaving you with 1 1/2 - so you now cut that strip at 1 1/2 inches.

Say you want to make that block one-quarter of the size:  Instead of the 2 1/2 inch strip, you would "remove" the seam allowance of 1/2 inch, divide the two inch measurement by four (into one-quarter) which equals 1/2 inch and add the 1/2 inch seam allowance back in, so you would then cut the strip at one inch.

How about if you want to double the size of that block?  Make it twice as big?  Remove the 1/2 inch seam allowance, then DOUBLE the two inch measurement, making it four inches, then add the 1/2 inch seam allowance back in - so now you would cut a 4 1/2 inch strip.

I hope this is making sense!  If not email me comments and I will try to answer your questions.  Above are two of my favorite rulers.  Sometime the math gets a little tricky.  In the examples I used everything divided or doubled rather nicely.  Sometimes you get into measurements in the 16th of an inch.  Both of the rulers above have 16th inch measurements.  And if the math gets TOO tricky, sometimes I get out the graph paper and just re-draft the block!  Then you can paper piece it, or make the math more do-able.

Re-sizing blocks for appliqué is much easier!  You just take the pattern, put it in the copy machine and select "custom size" and make it whatever size you want - no math involved.  (I like math though and I like the challenge - I think that's why I enjoy re-sizing blocks so much :)

Let me know if you have comments or questions and go re-size something - just for fun!