I think Raosoft online sample size calculator may be helpful. Please follow the linkhttp://www.raosoft.com/samplesize.html You will get detailed information about the process of sample size calculation in their page and this is a easy to use scientific tool.
It is well accepted as a reference tool to calculate sample size for a population based survey. For example you can check this article- Link: http://www.biomedcentral.com/1471-2431/14/20/