Welfare economics:

Welfare economics is a part of economics that uses microeconomic methods to evaluate economic well-being, especially related to competitive general equilibrium within an economy as to economic efficiency and the resulting income distribution related with it. It defines social welfare, however calculated, in terms of economic activities of the individuals that create the theoretical society considered. Accordingly, individuals, with related to economic activities, are the main units for aggregating to social welfare, whether of a community, a group, or a society, and there is no "social welfare" apart from the "welfare" related  to with its individual units.

Welfare economics typically takes individual preferences as provided and stipulates a welfare improvement in Pareto efficiency parts from social state A to social state B if at least one person prefers B and no one else opposes it.

There is no need of a unique quantitative calculate of the welfare improvement implied by this. Another part of welfare treats income/goods distribution, adding equality, as a further dimension of welfare.

Social welfare denotes to the overall welfare of society. With suitably strong assumptions, it may be defined as the summation of the welfare of all the individuals in the society. Welfare can be calculated either cardinally in terms of "utils" or dollars, or calculated ordinally in terms of Pareto efficiency. The cardinal function in "utils" is seldom used in pure theory today because of aggregation problems that create the meaning of the method doubtful, except on extensively challenged underlying theories. In applied welfare economics, such as in cost-benefit analysis, money-value calculations are often used, mainly where income-distribution effects are divided into the analysis or seem unlikely to undercut the analysis.