Bell-bottomed trousers became fashionable in the late 1960s. In more recent times, the style has returned to fashion in the form of flared trousers, with the difference being the size of the bell. Flared pant legs are smaller around than traditional bell-bottoms. Transforming regular trousers into bell-bottomed trousers requires only basic sewing skills and can be done with or without a sewing machine. After a few measurements and some basic alterations, you will have a pair of bell-bottomed trousers.
Turn the trousers inside out, fold the trousers in half vertically and lay them flat so the outer leg seam is visible. Center the outer seam and smooth out any wrinkles. Using the measuring tape, measure along this seam from the bottom hem of the trousers, to just below the knee. Mark this point with tailor's chalk. Measure the same length on the other leg. Mark that one too. Write down this measurement and label it "A."
Remove the seam by inserting the seam ripper's end into the threads at the seam and pulling up to open the seam. Or, carefully, cut only the thread of the seam with scissors until you reach the mark you made at the knee. Repeat on the remaining leg. Keep the fabric the seam was sewn to intact. If using scissors, cut directly along the seam to keep the edges straight.
Position the front and back of the pant leg so there is a triangular opening where the seam was. Measure the width of the triangle's base. Write down this measurement and label it "B."
Fold the fabric for your bell-bottoms in half. Take Measurement A, and add half an inch to three-fourths of an inch to that number. This is now your height measurement. Starting at the edge, mark the height measurement along the folded side of the fabric.
Divide Measurement B. This is your width measurement. Measure the width along the bottom edge of the fabric, starting from the folded side until it reaches the desired length. Add half an inch to the width length. Mark the fabric at the new width measurement with tailor's chalk.
Use a straightedge ruler to draw a line connecting the two marks. Make sure your line is straight and the folded fabric is flat and wrinkle free. Pin the two sides of the fabric together at the top, the middle-bottom and close to the chalk line to ensure that they do not move.
Use scissors to cut along the chalk line. When you finish, unpin and unfold the fabric. You should have a triangle. Use this triangle as a guide for a second, identical triangle. Use the same folded fabric method, but instead of measuring, simply fold the first triangle around the fabric and trace the line from the corner to the top onto your uncut fabric. Remove the first triangle, pin the two sides together and cut. You should have two identical fabric triangles.
Measure half or three-quarters of an inch on your bell-bottomed fabric, depending on how much extra fabric you added at the bottom. Fold that amount of fabric under and pin it perpendicular to the edge to make a hem in your fabric. Do this for both triangles.
Pin the top point of the fabric triangle to the top point of the opening in the leg of the trousers. Since the trousers are inside out make sure the backside of your fabric is toward you. Removing the seam should have left a folded, fabric edge on either side of the opening. Fold the side of your fabric triangle like you did when creating the bottom hem. Then, starting from the top, pin the folded edge of the trousers to the folded edge of the fabric together, ending at the bottom.
Check that the bottom corners line up and, the bottom edge is even, then sew the new fabric to your existing seams. Use the pins as guides to keep your seam straight. Repeat the same process the other side and on the other leg.
Secure any loose ends, turn the trousers right-side out and admire your new bell-bottoms.
Make sure you have a workspace with enough room to lay your trousers out flat. The floor will work if there is no surface available. Also make sure the tools you will need are nearby. If possible, use a sewing machine instead of hand sewing. The sewing machine will make your seams more durable and straight. If you hand-sew, use an overcast stitch to attach the raw edges of the fabric together, followed by a straight stitch at the base of the folded fabric. Write down all measurements because in most cases you will be using them in later steps. Once the bell-bottoms are complete you should send them through the washer and dryer to test the newly sewn seams' durability. Make sure you have enough of the same fabric for both pant legs.
Be careful when ripping the seams out of the trousers to preserve the fabric. You will need this fabric later in the project so try to keep it free of tears and holes. Try to use fabrics that are a similar weight to the material of the trousers. Mismatched fabric weights can cause tears.