Summarize the following:
The majority of women are wearing the wrong sized bra. If your bra isn't the right size, then you will have trouble putting it on because it won't fit your dimensions correctly. Here are some easy signs that say that you're wearing the wrong bra:  If your breasts spill out of the top of the bra. If the straps or band of the bra cut into you. If the bra feels incredibly tight—like you can't breathe in it. If the bra is so loose that the straps fall down no matter how much you adjust them. If you can comfortably fit two fingers between your side and the band of the bra. To get an idea of your band size, measure your under bust in inches, making sure the tape is snug, but not tight. If it is below 30" (76 cm), round up to the nearest even number. If it is above 36" (91 cm), round down. This is your band size If your under bust measures over 36" (91 cm), take a bust measurement while lying on your back. Average the two bust measurements, then calculate the cup size. To work out the cup size, lean forwards at 90 degrees and measure your bust loosely. Take the difference between the bust and under bust measurements, and convert into cup letters. For example, an A cup has a 1" (2.5 cm) difference, while a B cup has a 2” (5 cm) difference. This is the best thing to do if you don’t feel confident measuring your own bra size. Independent boutiques are generally the best places to get fitted because the fitters are specially trained. Department stores are generally not the best places to get fitted, as the employees often aren't trained well and sometimes use outdated measuring techniques. Go to several places to get a bra fitting done before purchasing a bra. You may have thought that you were a 36C all of your life, only to be told that you're really a 34D. Don't reject the measurements if the bra fits comfortably. Instead, try wearing a bra in the correct size and see how much better you feel. If you really aren't sure about the results of the fitting, try on as many bras as you can, or get another opinion from a professional. There are a variety of reasons the size of your breasts can change. Your size could change because your body is still growing, because you've experienced significant weight loss or gain, or if you're pregnant. Measuring regularly is a good habit to keep up if you want to wear the right bra and be able to put it on correctly.

Summary:
Look out for obvious signs that your bra is the wrong size. Measure your band size. Measure your cup size. Go get a professional fitting. Trust the measurements. Measure your size once a year.