Marine space is overall under increasing pressures from human activities. Traditionally, the activities taken place in oceans and seas were related to fisheries and transport of goods and people. Today, offshore energy production – oil, gas, and wind, aquaculture, and sea-based tourism are important contributors to the global economy. This creates competition and conflicts between various uses and requires an overall regulation and planning. Maritime activities generate pressures on the marine ecosystems, and in many areas severe impacts can be observed. Maritime spatial planning is seen as an instrument to manage the seas and oceans in a more sustainable way, but information and tools are needed. The current paper describes a tool to assess the cumulative impacts of maritime activities on the marine ecosystems combined with a tool to assess the conflicts and synergies between these activities.