Subjective well-being (SWB) is a concept of well-being (happiness) that focus on evaluations from the perspective of the people who's lives are being evaluated rather than from some objective viewpoint. SWB measures often rely on self-reports, but that does not make them SWB measures. Objective measures of wellbeing are also sometimes measured with self-reports and SWB can also be measured with informant ratings.

Ed Diener defined SWB in terms of three indicators of subjective well-being: frequent positive affect, infrequent negative affect, and cognitive evaluations such as life satisfaction.

SWB includes two different subjective measures of well-being that are based on different definitions of happiness. Experiences of positive affect (mood, emotions), and experiences of negative affect (mood, emotions) can be used to create a measure of the amount of positive and negative affect in people's lives. These hedonic balance scores measure subjective wellbeing from a hedonistic perspective that define happiness as high PA and low NA. Life-satisfaction is based on a subjective view of happiness. Accordingly, there is no objective way to define happiness and people have to define it for themselves. They then use their own definition of happiness to evaluate their actual. Therefore SWB is not a definition of happiness. Rather it is a label for two definitions of happiness, a hedonistic one and a subjective one. Both are based on subjective experiences, but the subjective experiences are different. Hedonism relies on aggregation of momentary affective experiences. Life-satisfaction relies on the recall and evaluation of past experiences.

Although SWB tends to be stable over the time and is strongly related to personality traits, the emotional component of SWB can be impacted by situations; for example, the onset of the COVID-19 pandemic, lowered emotional well-being by 74%. There is evidence that health and SWB may mutually influence each other, as good health tends to be associated with greater happiness, and a number of studies have found that positive emotions and optimism can have a beneficial influence on health.

Diener argued that the various components of SWB represent distinct constructs that need to be understood separately, even though they are closely related. Hence, SWB may be considered "a general area of scientific interest rather than a single specific construct". Due to the specific focus on the subjective aspects of well-being, definitions of SWB typically exclude objective conditions such as material conditions or health, although these can influence ratings of SWB. Definitions of SWB therefore focus on how a person evaluates his/her own life, including emotional experiences of pleasure versus pain in response to specific events and cognitive evaluations of what a person considers a good life. Components of SWB relating to affect include positive affect (experiencing pleasant emotions and moods) and low negative affect (experiencing unpleasant, distressing emotions and moods), as well as "overall affect" or "hedonic balance", defined as the overall equilibrium between positive and negative affect, and usually measured as the difference between the two. High positive affect and low negative affect are often highly correlated, but not always.

There are three components of SWB: affect (hedonic measures), life satisfaction (cognitive measures), and eudaimonia (a sense of meaning and purpose). Current research recognizes the importance of accurately assessing SWB within a society by focusing on how each component of SWB impacts the individual.

Affect refers to the emotions, moods, and feelings a person has. These can be all positive, all negative, or a combination of both positive and negative. Some research shows also that feelings of reward are separate from positive and negative affect. Research also recognizes that when evaluating subjective well-being, approaches to affect can be interchangeable between children and adults.

Life satisfaction (global judgments of one's life) and satisfaction with specific life domains (e.g. work satisfaction) are considered cognitive components of SWB. The term "happiness" is sometimes used in regards to SWB and has been defined variously as "satisfaction of desires and goals" (therefore related to life satisfaction), as a "preponderance of positive over negative affect" (therefore related to emotional components of SWB), as "contentment", and as a "consistent, optimistic mood state" and may imply an affective evaluation of one's life as a whole. Life satisfaction can also be known as the "stable" component in one's life. Affective concepts of SWB can be considered in terms of momentary emotional states as well as in terms of longer-term moods and tendencies (i.e. how much positive and/or negative affect a person generally experiences over any given period of time). Life satisfaction and in some research happiness are typically considered over long durations, up to one's lifetime. "Quality of life" has also been studied as a conceptualization of SWB. Although its exact definition varies, it is usually measured as an aggregation of well-being across several life domains and may include both subjective and objective components.