First let's do a little bit of math calculations and measurements. Measure your waist and divide by 3.14 to get the waist radius (inner circle). Round up to the nearest inch.
Measure your waist and divide by 3.14 to get the waist radius (inner circle). Round up to the nearest inch.
Measure the desired skirt length and add it to the waist radius to get the hem radius (outer circle).
Check the stretch in your fabric. You'll want the stretch to go sideways.
Depending on the stretch, fold the fabric in half (stretch will need to be perpendicular to the fold).
Take your measuring tape and pin it at the fold, on the left hand side corner.
Measure out from this corner, using your waist radius and moving the tape and marking right at the radius number to create a circle
Repeat for the hem radius using the hem radius number.
Cut fabric along the circles.
Pin the raw sides and sew down using a regular stitch and a kit or jersey needle. Use a walking foot to make sewing knits easier. If you don't have one, adjust the presser foot tension to minus (see here how to change the settings in your presser foot tension). A looser presser foot will allow the knits to slide through easily without stretching. Test on a piece of fabric to get the best tension fot your project.
Finish side seam with a serger or a zig zag stitch or just leave as is, knits won't fray.
Cut a piece of fabric for the waistband. You'll need it to stretch it sideways. The waistband should be 5 inches tall, and your waist measurement wide, adding 1/2" seam allowance.
Place the ends of the waistband together, right side together, pin and sew down the raw edges, leaving a small gap in the middle, to thread the elastic through later on.
Fold the waistband in half, turning it right side out and press.
Turn the skirt right side out, slide the waistband over the top of the skirt and pin the raw edges together. Make sure the opening in the waistband is facing out. Also make sure the seam in waistband matches the seam in your skirt.
Sew the waistband to the skirt. Make sure you are using a stretch or zig zag stitch here so the waistband will stretch over when taking it on and off. Finish raw seam with a serger or zig zag stitch or just leave as is.
Flip waistband up and press.
Decide how tight you want the elastic.
Using a safety pin, thread the elastic through the waistband, trim, pin the ends and sew with a zig zag stitch.
Using a ladder stitch, close the gap in your waistband.
Hang the skirt over night. Since you are cutting some of the fabric on the bias, some parts of the skirt might stretch out a little more than others and it's best to know that before hemming.
Also before hemming knits, is best to stabilize the hem so it won't stretch while sewing. You can use knit tape if you have or use very thin and stretchy interfacing. Make sure the stretch in your interfacing goes with the stretch in your fabric. A stabilized hem won't pucker or stretch while sewing so you will get a smooth finish.
Press the hem up using an up and down motion of your iron to avoid stretching the hem.
You may need to adjust the presser foot tension to an even lower tension for hemming your skirt. Test on a piece of fabric first. Sew down the hem using a regular straight stitch.