"Poverty Line" is the main concept of Poverty.
Poverty Line is a common method used to measure the poverty, and it is based on the income as well as consumption level. It is an imaginary line that is considered appropriate for its existing level of development and its accepted minimum social norms. It differs from place to place (or country to country) with time. A person is considered to be "poor", if he/sh can't fulfill his/her family's basic needs (like housing, clothing, food requirement, education, medical facilities, footwear, fuel, light, electricity, etc.) through his/her monthly income.
While determining the poverty line in India a minimum level of basic needs are determined for subsistence.These needs are multiplied by their prices in rupees. The present formula for food requirement while estimating the poverty line is based on the desired calorie requirement. the calorie requirement vary depending on age, gender and the type of work the person does (e.g. in India, in rural areas, calorie requirement is 2400 calories per person per day. While in urban areas, calorie requirement is 2100 calories per person er day.).
The poverty line is estimated periodically (normally after every five years) by conducting sample surveys. These surveys are carried out by the National Sample Survey Organization (NSSO). However, for making comparisons between developing countries, many international organizations like the World Bank use a uniform standard for the poverty line : minimum availability of the equivalent 1 USD per person per day.