Measure the distance the waist band is gapping. You can pin jeans how you'd like them to fit at the waste and double the and measurement of the excess cloth.
Take out the seam between the waistband and the yolk of the jeans at the back.
Separate inner and outer waistband. Make the new seam and adjustment of size at he back seam of waistband hidden by back center button loop. (see picture above) Sew the outer/inner band of the waistband and trim excess cloth. Then finish upper seam of waistband leaving the bottom seam open -to be sewn to yolk.
In the yolk, make darts so top of yolk will match measurement of the now smaller waistband.
Darts were placed at an even distance away from the center seam.
Try jeans on and mark where the waistband falls horizontally on the yolk. Leaving a seam allowance you can trim this fabric above the marking.
Insert the yolk into waistband and pin. Try on jeans to ensure fit. Stitch waistband.
