There might be a day when you are in need of a sports bra but haven't packed one and won't be able to get to a store to purchase one new. A sports bra can be constructed quickly at a very low cost with a little ingenuity and some basic cutting and sewing skills.
Select a pair of briefs that you'll use for your bra. Make sure the waistline of the underwear will fit around your ribs comfortably.
Lay the underwear flat on a table with the elastic waistband facing away from you. Smooth out any wrinkles in the underwear.
Notice the seam lines on either side of the crotch of the underwear. You will be using these lines as initial guides.
Pick up your scissors and cut into the crotch area approximately 1/2 inch away from one of the side seams. You are beginning to cut the hole that your head will eventually go through. Leave material by the seams to give you room to hem the material for a smoother look on the neckline.
Separate the front and back of the crotch material you just cut. Cut the front part of your material in a semicircle between the seams, finishing the cut by guiding it approximately 1/2 inch from the opposite seam from where you started.
Flip the underwear over and continue cutting along your initial cut in a semicircle for your back. Do this the same way you did the front, but make the semicircle slightly smaller because the back of a sports bra is generally higher than the front.
Tuck under the rough cut edges and pin them to create a smooth neckline. Iron the material so it is flat and smooth for easier sewing.
Use needle and thread to make small hemming stitches. Slip your head through the hole in the crotch and slip your arms out the leg holes to test out your freshly made sports bra.