To calculate the put-call ratio one needs to check the open interst of puts and calls and divide it! But we have different puts and different calls so how it is calculated?

General
2

Do not do so much math, just type nifty put call ratio live on google even in live market, iifl site came , open it , there the ratio

3

Sum of the total OI of different Put and calls. An excel sheet for OI analysis with realtime update from NSE.
https://www.facebook.com/download/1623525171256576/NIFTYmain.xlsm

4

PCR is a ratio of Traded contracts, i.e, it is ratio of Put volume by Call Volume (not Open Interest). Also, multiple strikes of Puts + Calls, as well as different calender month contracts are taken for calculating PCR.

http://www.investopedia.com/ask/answers/06/putcallratio.asp

Also, there are several types of PCR.

http://www.cboe.com/publish/oicommentary/rr_11_24_11.pdf

5

Not OI . .volume.