Trousers that are too long can often drag on the ground and wear much more quickly than those that are hemmed to the proper length. The best way to prevent frayed cuffs is to ensure that your trousers fall about 2.5 cm (1 inch) above the back of your shoe. If you do have frayed cuffs it is possible to extend the life of your trousers with a simple repair job.
Lay out the trousers with the frayed hem on a flat surface and smooth them out. Using a washable marker make a mark on either side of the trousers where the fraying stops.
Fold the hem of your frayed trousers under, or if they're long enough, cut off any excess first and then fold under. Use your marks on each side of your trousers as your guideline for how much to fold under.
Flip the trousers inside out from about the knee down. Follow the top of the turned up cuff and sew it onto the inside of the trousers. You can start by doing a few stitches on both sides and then do the final stitching. If you have a sewing machine, you can use it for a more polished seam. Otherwise, hand stitch carefully from the inside with the same colour thread as the pant.
Flip the trousers outside in and adjust your iron for the appropriate setting for the material. Iron along the cuff until it's flat. You now have trousers that are adjusted to the correct length without fray.