|Andreas Rentz/Getty/www.people.com Ryan Reynolds|
If you are getting your shirts custom made (which I highly recommend), your tailor will add about a 1/4" to your actual "skin measurement" to allow for some movement.
Wearing a shirt that doesn't fit properly looks unprofessional and thrifty. If you are not going to have your shirts made, go to a tailor and ask if you can compensate them to give you your measurements so that you know your off-the-rack shirt is the appropriate size. Bottom line is, if the shirt fits, and only if it fits, wear it.