If we aim to increase the sustainability of farming, we must be able to measure the sustainability of individual farms and relate this sustainability to the characteristics of the farm and its management. We hypothesized that (i) sustainability can be expressed using social profit, and (ii) socio-economic characteristics and management practices of farms explain differences in sustainability. The objective of our work was to provide empirical evidence for these hypotheses. Data was collected data over two years from 361 coffee farms in Vietnam to calculate social profit. We found that the average social profit of farms was 2300 USD. The main source of social profit inefficiency is the sub-optimal allocation of resources and levels of production. Statistical association between the set of socio-economic characteristics and management practices and social profit inefficiency shows that social profit inefficiency is increased (sustainability is decreased) by larger distances from the coffee farm to the closest town/city center and to the closest coffee factory/traders and by a high frequency of spraying. On the other hand, sustainability is increased when coffee producers belong to the ethnic group JoRai, when using more hired labor and frequency, and when there are a larger number of fertilizing and pruning activities. We conclude that social profit inefficiency can be used to summarize sustainability.