Varies based on beer- you can look it up on MFP or just Google it, usually, unless it's a more obscure craft beer.  Guinness stout is one of the lowest calorie beers you can get at about 120cal/12oz, most are anywhere from 130-200cal/12oz.  There are some "diet" beers out there (like MGD 64) but they taste like someone took shitty beer and diluted it with water (and "light" beers are like "light" olive oil- the "light" refers to the strength of the flavor, not that they are lower in calories).  I absolutely love craft beers and trying new kinds, so I'm always checking online for calorie counts to make sure I'm not going overboard having 1-2 with dinner every now and then. (*edited to correct calories in Guinness)