You will need: Fabric for front and back of cozy; Matching or contrasting thread; Batting (insulated or non-insulated); Buttons; And elastic hair ties.
Start by measuring the width of the cup. Choose the widest part near the middle. I measure my mugs through the handle as that is where the cozy will snuggle the mug. This will give you the length of the fabric. Remember to add seam allowances. Since this craft doesn’t require the cozy to be strong, I only used a quarter inch seam allowance on each side for a total of an extra half inch.
Then measure the height of the mug. This will give you the width of the cozy. Remember to add seam allowances. Again, I only used a quarter of an inch on each side.
Cut your fabric into 2 strips based on your width measurement (plus seam allowance) and the length measurement (plus seam allowance). Cut batting into strips based on width and length measurements without seam allowances. So your fabric will be bigger than the batting.
Place fabric right sides together. Center your batting on the top fabric (this should be the wrong side up) and pin in place. (It doesn’t look like it in the photo, but there is a seam allowance on the other side that doesn’t show.)
Sew lengthwise alone one edge of the batting approximately 1/8 of an inch from the edge of the batting. Trim off excess seam allowance. Trim up to the batting.
Turn the fabric pieces over so they sandwich the batting. The right sides should now be facing out. Fold the bottom fabric over the batting and pin in place. Then fold the top fabric so the folded edge meets the bottom fabric fold. Pin in place.
Sew lengthwise along the edge approximately 1/8 of an inch from the edge to stitch the side closed. I use the quarter inch foot and move the needle so that it sews 1/8 of an inch from the edge.
Now your cozy should be a tube open on both ends.
Fold the edge under ¼ of an inch so you will have a finished edge. Pin in place. Center the elastic band and pin in place. I found it easier to use one center pin to keep the elastic in place and two pins on the sides to keep the band closer to the center spot. Sew approximately 1/8 of an inch from the edge to seal the edge and to secure the elastic band.
Next add the button(s). Place the cozy around the mug and stretch the elastic to a point where it will hold the cozy snugly, but not too tightly. Mark that spot with a pin or marking pencil. Sew a button to that spot. I included a second button for decoration and also so I could use it with another sized mug.
The cozies can be angled on the ends so they fit through the handle better. I thought that the asymmetrical shape of this one would help it fit into the handle and keep it centered on the mug.
Here are the three mug cozies that I created today. The ends on each are different so I can experiment and decide which works better. They make inexpensive gifts. Embellishments and embroidery would personalize each. (I need to save up for an embroidery machine.)
Here is the finished product with the mug.