Livestock farming systems are criticised for their environmental impacts, but they can also provide various ecosystem services to society, especially permanent grasslands. This study aimed to develop a method to assess impacts of permanent grasslands and their management on the supply of regulation and maintenance ecosystem services applicable at the field and/or farm level. To this end, an existing framework, the Ecological Focus Areas Calculator, was adapted to (i) consider attributes and location parameters of permanent grasslands and (ii) integrate impacts of permanent grassland management on the provision of ecosystem services, which yielded a score for each ecosystem service. The method developed was tested with two farms. Analysis of mapping results, which calculated a score for each ecosystem service for each permanent grassland field on each farm, highlighted the direct relation between the novel approach and the underlying ecological theory of impacts on ecosystem services. On each farm, management practices influenced ecological processes differently, which led to different changes in ecosystem service scores. Applying this novel approach directly with farmers can help them identify win-win situations and trade-offs and target their management, by identifying the fields where it may be more optimal to focus certain management practices to decrease the farm's overall impacts based on trade-offs at the individual-field scale. The novel approach combined representation of the complexity of interactions between management practices and ecological processes with the ability to provide results that are easy to use and interpret. Future development could help increase the accuracy of estimated impacts of management practices on ecosystem services, such as by adding additional practices or considering their long-term effects on ecological processes. The novel approach could also be updated to assess impacts of other types of land use, such as arable land, or management practices. The final goal of such a tool is to support decision-making to optimise the ecosystem services supplied by farming systems, which has advantages for society and for farmers.