It isn’t much fun to wear too-tight jeans that cut into your waist and give you muffin-top. Even jeans that fit just right can end up shrinking when you wash them, but you can stretch them back out. Most jeans can be stretched up to a size or two. Wet jeans are easier to stretch than dry jeans, so the best time to stretch them is as soon as you take them out of the washing machine. Skip the dryer, and go right to the stretching steps.
A pants stretcher is kind of an old-fashioned device that is regaining popularity because it works. Slide the pants stretcher into the wet jeans. Position the stretcher so the denim is smooth and pulled tight. the stretcher out until the fabric is pulled tight. Then, set the stretcher’s clasp. Hang the jeans up to line dry, and do not remove the stretcher until they are completely dry.
Another way to stretch the width of your jeans is to put them on wet, just like they did in the old western movies. It won’t be the most pleasant sensation, unless you like wearing wet clothes; but the jeans will be molded to fit your hips and legs. It might also seem like It takes the jeans a very long time to dry, but you can cut the time by standing near a fan or a heat register. Make sure you move around a lot, to get a thorough stretch on the tight areas.
If you find your jeans shrinking lengthwise, it is because of the way the fabric was cut, and stretching them will be a little bit harder, but you can get a little bit of length back. When the jeans are fresh out of the washer, not dripping wet, but before you dry them at all; stand on the hem and pull up on the inseam. The inseam will usually be the toughest to stretch because of the type of seam used. Then pull up on the waist-band. This might start an unwelcome circle, though. To stretch the outer seam; you will probably lose a little bit of width when the jeans stretch, so then your jeans may be snug around again.
Sewing and Craft Alliance: Denim … More Than Just a Pair of Jeans
Iowa State Extension: Consumer Choices: Textile Labels
Ohio State University Extension: Selecting Jeans