To measure your neck, place the tape measure around the base of your neck, just below the Adam's Apple. This is where your shirt collar will typically sit. Be sure to leave a small gap (about the width of one finger) between your neck and the tape, so the collar isn't too tight when fastened. If you're uncertain about your size, it's better to round up to the next quarter-inch. Generally, your neck measurement aligns with your shirt size, so a 15.5" neck means a size 15.5 shirt.

Start by raising your arms slightly and wrapping the tape around the fullest part of your chest. Once the tape is in place, relax your arms and let them fall naturally. Make sure the tape measure stays level across your chest and doesn't ride up or sag on your back. If you’re unsure, round up to the nearest quarter-inch for accuracy.

For your waist, position the tape measure just above your belly button, around the natural waistline. If you have a more prominent stomach, make sure to measure at its fullest point. Keep the tape level across your midsection, ensuring it isn’t too high or low. Again, round up if you’re in doubt about your measurement.

Begin measuring at the center of your back, where your neck and shoulders meet. You should be able to feel the bony part of your spine. Run the tape across your shoulder and down your arm, ending at the meaty part of your palm. The tape should follow the natural curve of your arm. When unsure, round up to the nearest quarter-inch for accuracy.

For the shoulders, stand relaxed with your arms at your sides. Locate the outer edges of your shoulder bones—start with your left shoulder, then measure across to the right one. Measure the distance between these points, following the natural curve of your shoulders, and ensure the tape forms a gentle arch. If you’re unsure, round up to the nearest quarter-inch.