A well-fitted shirt is essential to any man's professional attire. Collar measurment is very important, as a tight collar makes you feel like you're choking and a loose one looks sloppy. You also need your shirt collar to fit properly so your tie will look good. If you are not sure what size a shirt collar is, you can measure it to determine the size and see if it will fit you.
Wrap a tape measure around your neck right above the clavicle (collar bone).
Note the measurement where the end of the tape measure doubles around and meets itself.
Add 1/4 inch to the measurement from Step 2.
Round up the result from Step 3 to the closest half inch. For instance, if you measured 16 inches around your neck and added 1/4 inch, that would give you 16 1/4 inches, which you would then round up to 16.5 inches. This is your shirt collar size.
Place a shirt on a flat surface so that the collar is lying open and flat.
Place a tape measure on the inside of the collar. Measure from the collar button to 1/8 inch away from the far end of the button hole on the other side. If the measurement is the same as your shirt collar size, the shirt will fit you properly.