The government of India uses a consumption based method to measure poverty: given that an average adult male has to eat food representing approximately 2000-2500 calories per day in order to sustain the human body, how much would it cost to buy these calories? Those who have an income that is lower than this cost, are poor.
Actually, the Indian government uses the thresholds of 2,400 calories a day in rural areas and 2,100 in urban areas. (City dwellers are thought to exert less energy, so they should need to consume less. See here).
Of course, this measure, like all measures, isn’t perfect. A person may be able to afford to buy food that contains 2,400 calories, but the quality or nutritional value of this food (in terms of vitamins etc.) may be so low that we can hardly exclude this person from the population of the poor. He or she may be able to buy 2,400 calories, but not enough nutritional value to lead a decent life.
However, I wonder whether India’s poverty measurements include only consumption of food. Poverty is more than just a nutritional issue. People may be able to buy enough food of sufficient nutritional quality, but may be left without resources for shelter, healthcare, education etc.