Use this spreadsheet to determine the extent of portfolio overlap among your equity mutual fund holdings. The tool can help you build a well-diversified equity portfolio. The sheet extracts mutual fund portfolios from money control and compares stock holdings.
Update Aug 30th 2016: There was an issue with the way in which the percentage overlap was reported - the answer would change if fund A and fund B was interchanged. This embarrassing error has now been corrected. Thanks to Arshi Ahmed Khan for pointing this. Other readers had also mentioned this earlier but it is only now that I found a consistent way to correct it.