You can use web tools that make such estimation.<p>Examples:<p><a href="http://www.similarweb.com/" rel="nofollow">http://www.similarweb.com/</a> (best one in my opinion)<p><a href="https://www.compete.com/" rel="nofollow">https://www.compete.com/</a><p><a href="http://www.alexa.com" rel="nofollow">http://www.alexa.com</a>