It is important to measure the high bust area snugly (like a skin measurement) to pick your proper size. If you measure loosely, your garment will be too big!
Pick Your Size: Take two bust measurements - high bust and full bust. Choose your pattern size by the high bust measurement. You may be picking a size that is smaller than normal, but you'll get a very nice fit through the shoulder and armhole areas.
High Bust - just under the shoulder blades, as high as possible under your arms, above the fullest part in the front.
Full Bust - Straight around the fullest area.
This pattern has two different Front pieces. If there is less than a 3" difference between your high bust and full bust measurement, use the basic Front pattern piece. If there is more than a 3" difference, use the Darted Front pattern piece. If you are "on the fence", try your first T-Shirt using the Darted Front, and the second using the basic Front.