Wash the jeans in cold water. If using a washing machine, set the cycle to normal. Warm or hot water can cause shrinkage or color bleeding. Remove the jeans from the wash, and turn them inside out.
Place a towel on the floor. Lay the jeans flat on top of the towel, with the legs extending away from you. Standing over the jeans, put one foot on the waistband.
Reach down and use both hands to grab the inside and outside seam of one of the legs, just below the crotch. Tug the jeans toward your body maintaining constant tension. Make certain that you are only pulling lengthwise on the fabric and not widthwise.
Move your hands 6 inches down the leg of the jeans. Again, pull the jeans towards your body, while holding onto the side seams.
Move your foot onto the top of the leg and move your hands down the jeans another 6 inches. Continue pulling the material and moving your hands and foot down the leg of the jeans, maintaining an approximate 1-foot distance between your hands and your foot as you tug.
Repeat this process on the other leg of the pants.
Allow the jeans to air-dry, and then assess the length to determine if you have stretched the jeans enough. If not, repeat Steps 1 to 6 until you have reached the length that you desire. Keep in mind that you typically can gain only 1 to 2 inches of length by stretching this way.