title: Is there a formula to estimate index size in InnoDB?
body: <p>How is it possible to calculate index size for specific column types in InnoDB i.e.:</p>
  
  <ul>
  <li>VARCHAR</li>
  <li>CHAR</li>
  <li>TIMESTAMP</li>
  <li>SMALLINT</li>
  </ul>
  
  <p>I've found a formula for MyISAM (<a href="http://dev.mysql.com/doc/refman/5.7/en/key-space.html" rel="nofollow">http://dev.mysql.com/doc/refman/5.7/en/key-space.html</a>): (key_length+4)/0.67</p>
  
  <p>Does this work for InnoDB as well? </p>
  
  <p>I'm trying to estimate the size of a database I'm designing for sizing purposes.</p>