Make a new sports-type bra from a pair of large panties for a comfortable bra for exercising and lounging around the house. If you prefer something a little bit sexier than a functional undergarment, you can turn an old pair of bright-coloured cotton or satin underwear and a little bit of decorative elastic into a string-type bra to wear underneath a white or light-coloured top. Double-up the layers for the bra and wear the string bra as a bikini top for a trip to the beach.
Cut the straps for the bra. Measure the circumference of your chest, just beneath your bust line. Add about 20 inches to the measurement and cut a piece of decorative elastic trim to this measurement. Cut two additional pieces of the elastic trim, each to a length of about 20 inches.
Lay the large underwear on your working surface with the front facing forward and pin the two layers of the fabric to keep them together.
Draw a triangle on the underwear. Make the triangle about 10 inches wide and 8 inches tall. Cut through both layers as you cut out the triangle shape.
Lay the triangles side by side with the wrong side facing upward and fold over the top point of each triangle. Place the end of one 20-inch-long piece of elastic over top of the fold and pin them to the fabric.
Fold over about 1/4-inch of fabric along the left and right sides of the triangles and sew the folded fabric in place, while sewing stitches through the elastic trim to join it to the bra.
Fold the bottom edge of the bra upward 1 inch and sew the fold in place. Sew away from the fold line to create a tube at the bottom of each triangle.
Insert the remaining piece of elastic trim through the tubes in both of the triangles to make the cups for the bra. Tie the ends of the elastic behind your back and the two pieces of elastic at the top of the triangles behind your neck.
Lay the large pair of underwear front side down on your working surface.
Measure about 3 inches from the crotch of the underwear and make a line across the underwear, stopping just before the elastic side seam on each side.
Turn the line into a curved line by bring the ends of the line upward slightly.
Cut out the material in between the elastic seams. Start at the top of the crotch of the underwear and cut down, about 1/4-inch away from the elastic seam on the right. Cut down along the curved line, around the bottom of the line and back up the other side of the crotch of the underwear, about 1/4-inch away from the elastic seam on the left.
Try on the new bra.