Select the size that best matches your largest measurement (bust, waist or hip). If you're between the sizes, it's usually best to order the larger size so you have room to move, or some alterations can easily be made.
Let your arms hang naturally at your sides. Have someone measure you with the measuring; tape parallel to the ground. Have your friend measure under your underarms, around your back and over the fullest part of your bust. Make sure the measuring tape is snug but not tight.
Bend over to one side to find the spot; where your waist naturally creases. Measure this spot; it should be right under your nave l. Keep the measuring tape parallel to the floor and snug against your skin, but don't pull it tight.
Stand up straight with your feet together. Have a friend measure over your hips and rear, around the fullest part. Make sure to keep the measuring tape parallel to the floor.