Current Nifty PE Ratio on 25-May-2016 is 22.07.
Nifty PE ratio measures the average PE ratio of the Nifty 50 companies covered by the Nifty Index. PE ratio is also known as "price multiple" or "earnings multiple". If P/E is 15, it means Nifty is 15 times its earnings. Nifty is considered to be in oversold range when Nifty PE value is below 14 and it's considered to be in overvalued range when Nifty PE is near or above 22. The market quickly bounces back from the oversold region because intelligent investors start buying stocks looking to snatch up bargains and they do the exact opposite when Nifty P/E is in the overbought region.
Since NSE started, every time when Nifty's Price/Earnings ratio exceeded 22, the average return from Indian equities over the subsequent three years became negative.