Only 46.9% of the 246.6 million households have lavatories while 49.8% defecate in the open. The remaining 3.2% use public toilets.
Census 2011 data on houses, household amenities and assets reveal that 63.2% of homes have a telephone.
Analysts say the data show the complex contradictions of the Indian system.
They say the census reveals a country where millions have access to cutting-edge technology and consumer goods but a larger number of poor who lack access to even basic facilities.
About 77% of homes in the eastern state of Jharkhand have no toilet facilities, while the figure is 76.6% for Orissa and 75.8% in Bihar. All three are among India’s poorest states with huge populations which live on less than a dollar.
The census figures also show changes in how people access information and entertainment.
More than half the population – 53.2% – have a mobile phone.
The data show that 47.2% of households have a television while only 19.9% have a radio.
And the reach of computers with internet access is still miniscule, with only 3.1% of the population connected