Hello,
From first principles
Population density means Population Divided Geographical Area.
To compute area we need boundaries or the areas directly.
I feel the Area or the boundary of a Pincode number is not available. May not be reliable.
Population is also not available Pincodewise.
But you have Population and area of villages Precisely in census Data.
There are about 6.5 lakh Villages and Data for them is available.
Latest Pincode directory has about 1.5 Lakh entries containing about 19000 Pincodes from
Data.gov.inIf you really want to work at Pincode Level then you will need to figure out how to link these to Data sets.
I am not mentioning any specific source because it is confusing.
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If you are going by District Data then you are not going at Pincode level. My guess ...
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To the Best of my knowledge Census of India Villagewise areas are available only for 2001 census. Same data for 2011 is not released yet.