Men's shirt sizing isn't always clear cut, especially when you're used to looking simply for small, medium or large. Knowing your measurements takes the guess work out of shirt shopping and helps you find the right fit every time.

Dress-shirt sizing typically features two numbers that represent key measurements.

The first number on a shirt label indicates your neck size. Measure your neck at the Adam's apple level. Add about a 1/2 inch to the measurement, which will ensure your dress shirt isn't too snug.

The second number in dress-shirt measurements represents your arm length. This measurement represents the length of your arm, from the center of the back of your neck to your wrist.

You've figured out that you're a 15 1/2 x 34 shirt size, but find yourself confused when you pick up a new brand and see a third measurement listed on the tag. Some designers also include a waist measurement when sizing shirts. Fortunately, you already know this number -- just check to see what size pants you're wearing. Again, when in doubt, size up.

You might also notice that your label includes a description of the shirt's cut. Choose one that best flatters your silhouette:

• Slim fit: Slim-fit shirts hug the body. When trying on this style, make sure you can pinch at least an inch of fabric in the chest and waist and that the shoulder seams hit at the end of the shoulder.
  
• Athletic cut: This style of shirt features a broad chest, shoulders and arms with a narrower waist.
• Regular cut: The standard style, regular-size shirts are looser than slim fit and should give you 2 to 3 inches of fabric to pinch in the chest and waist.
• Full cut: This style features a wider bottom of the shirt than the regular cut, giving more room in the waistline for men who carry weight around their midsection.

While fit does vary by brand, generally, you can take your neck and arm measurements and translate them into a standard small, medium, large or extra-large shirt size.

• Small: Men with a neck size between 14 and 15 inches and arm length of 32 to 33 inches usually wear a size small.
  
• Medium: Medium builds have a neck size between 15 and 16 and arms that measure 33 to 34 inches.
• Large: Large shirts are cut for men with necks that measure between 16 and 17 inches and arms around 35 inches long.
• Extra Large: Men with necks exceeding 17 inches and arms at least 36 inches long should wear an XL.