You can use CPI (Consumer Price Index)

Sir,

I have used cpi for inflation. But what do I take for purchasing power.

Thanks

Puchasing power parity is a better way to deal with to answer the level of both development and underdevelopment. If your study is restricted to the well-being of the people , say, for a community or for tribe then you can consider GDP per capita or GNI per capita as well as a proxy as the data is not available at micro level; otherwise, better not to go for proxy of PP.

You may want to look at the approach of Almas, Kjelsrud & Somanathan (2013). This is quite adapted to India.