Tailoring the hem of your own trousers can save you money. Purchasing a sewing machine to hem your trousers yourself is worth the initial cost of the machine. Knowing how to use your sewing machine and how to measure an inseam makes hemming your trousers with a sewing machine easy. Getting the length just right is the most challenging part of hemming a pair of trousers on a sewing machine. With careful measuring and patience, all your trousers will fit perfectly.
Turn the trousers inside out and remove the thread from the current hem. Iron out the crease of the old hem as much as is possible. The crease may not iron out completely, which is fine.
Measure your inseam from the crotch to just below the ankle. If you wear your trousers with shoes that have a significant heel, add enough length to the measurement so that the hem will fall about 3/4 inch to 1/2 inch off the floor.
Mark the measurements on the inseam of both legs with a fabric pencil. Fold the hems of the trousers all the way around and pin the fabric so it creates a temporary new hem. Place the pins in a downward direction so you are not poked by one when putting the trousers on to adjust the hemline.
Turn the trousers right side out and put them on. Adjust the length of both hems and pin as needed until they are a length with which you are comfortable. Try on the trousers with the shoes you would most likely wear, and make any further adjustments to the length.
Take off the trousers and turn them inside out again. Iron the folded creases to create new hemlines. Measure and mark a line 1 1/4 inch up from the folded hemline, all the way around the leg of the trousers.
Remove the pins, unfold the hem and cut the fabric on both legs of the trousers at the marked line. The crease you ironed into the trousers earlier stays in place even when unfolded. After cutting, refold the hem at the crease and pin both hems down again. The trousers are still inside out at this point.
Sew both hems 1/4 inch from the edge of the cut fabric, removing the pins as you sew. Use a tiny but loose stitch for your dress trousers to decrease visibility. Jeans and casual trousers don't require hidden hemlines.
Iron the hems again to press them flat and turn the trousers right side out to finish.
Pinking shears help prevent fraying but fabric shears work just as well.
Stitching the trousers too tight causes pulling, gathering and draws attention to the hem.