Over time, the majority of us are bound to put on some extra weight or, if you are still young, to simply grow. But that is no reason to throw away your favourite pair of trousers. Making trousers larger, otherwise known as "letting out," is a simple process if you have the right tools.
Remove the belt loop, if there is one, with your scissors or stitch cutters by cutting the stitching and not the belt loop.
Cut out the stitching over the centre seam, releasing the waist line as far as it will go.
Put your trousers on and take in the waist line to the right fit. Have someone pin the fabric in place and mark it with the dress makers chalk.
Rejoin the fabric with a sewing machine along the marked line, taking out the pins as you go.
Try on the trousers again. If they still fit, resew the marked line several more times to strengthen the seam and protect from embarrassing blowouts. If it is not a good fit, repeat steps 2-4.
Press the new seam flat with a hot iron.
Reattach the belt loop by sewing it in place.
Remove the stitching at the bottom of your pant legs by using scissors or stitch cutters.
Try on your trousers with a pair of dress shoes. Have someone fold up the excess fabric to the desired length. Hold in place with pins and mark with the dress makers chalk.
Sew along the marked line with a sewing machine, removing the pins as you go.
Put the trousers on again. If it is still a good fit, resew the marked line several more time to make the stitch strong. If it is not a good fit, repeat steps 1-3.
Iron the seam flat to finish off your alteration.
Ironing the seams which you will modify before beginning work on them will make the process easier and create a more professional look.
Always cut the stitching and never the fabric. Only a true professional should be making any alterations to the fabric. Dress trousers are made with extra fabric so that they can be let out. If trousers have already been let out, and the fabric used up, you may not be able to make them any larger.