How to Calculate the Number Needed to Treat and the Absolute Risk Reduction

A standards group of scientists and editors called the Consolidated Standard of Reporting Trials or Consort issued a statement in 2011 that recommends reporting both absolute and relative effect sizes for binary outcomes. So if studies don't publish number needed to treat or even absolute risk reductions, how are we supposed to easily calculate numbers needed to treat? Fortunately, it's already been done for us by NNT.com which looks at high quality meta-analyses of randomized control trials. The website actually rates aspirin for primary prevention as red, which they take to mean as not recommended. Most professional societies do recommend daily baby aspirin for higher risk groups.