The Rhapsody Joggers are fitted through the calves so it's important to have the right amount of stretch for this pattern. There is a stretch gauge located on the front pant leg pattern piece which you can use to measure the stretch percentage of your fabric.
The stretch required for this pattern is 50% crosswise grain. You do not need vertical stretch (lengthwise grain) for this pattern; however, you will be able to notice a difference in the way it feels in the calves depending on the vertical stretch of your fabric. Those with very little to none will feel more snug than fabrics that have 20%+ of vertical stretch. I will show you how to measure both below.
Let's start with crosswise grain (horizontal stretch) which is most important. Grab the front pant leg or just page 5 of the Rhapsody Joggers pattern pieces if you have yet to assemble the pattern.
Grab your fabric and fold knit along crosswise grain (selvage should be on the side and fold of fabric at the top).
Place two pins 4" apart below the fold of the fabric.
Holding knit firmly at both pins, stretch the fabric and note the distance stretched beyond its original length. This french terry knit from So Sew English has 60% stretch so it is perfect for the Rhapsody Joggers.
If you want to know the recovery of the fabric. release the pulled end of the knit. If the knit returns to its original location, it has excellent recovery.
This one recovered to 5%, so pretty close!
Again you do not necessarily need vertical stretch for this pattern, but they will feel a little different in the calves. Here is how to check the vertical stretch.
Grab your fabric and fold knit along lengthwise grain (selvage should be on the bottom and fold of fabric at the top).
Place two pins 4" apart below the fold of the fabric. Holding knit firmly at both pins, stretch the fabric and note the distance stretched beyond its original length. This fabric has approximately 25% vertical stretch.
This stretch gauge can be used to measure stretch for any pattern