1. Start
  2. Methodology
a ship with goods

Clean Shipping Index ranks vessels on environmental
performance beyond regulatory compliance

A thorough methodology developed into a straightforward online tool.

The basis of the Clean Shipping Index is a digital questionnaire covering vessels' environmental performance. The questionnaire is accessible, with no associated cost, for all shipping companies and does not require membership in Clean Shipping Index. The questions cover general information about the shipping company as well as vessel-specific information. A key point is that this process goes beyond existing regulations and covers vessels of all types.

Vessels are scored on the following parameters


  • Leads to acid rain which affects vegetation and freshwater bodies
  • Contributes to particulate matter (PM) pollution
  • Harmful for the human respiratory system


  • Creates smog and tropospheric ozone formation
  • Leads to acid rain which affects vegetation and freshwater bodies
  • Harmful for the human respiratory system


  • Most significant greenhouse gas
  • Caused by burning of fossil fuels
  • Leads to climate change


  • Creates environmental toxicity
  • Bioaccumulation in marine organisms
  • Pollutes the food chain

Water & waste

  • Operational discharges pollute the marine environment
  • Microplastics pollute the food chain

Particulate matter

  • Harmful for the human respiratory system
  • Ultra-fine particles enter the cardiovascular system

The results

Final scores for vessels are based on the outcome of the questionnaire. A total of 150 points can be obtained, 30 points for each of the 5 different parameters. The final score results in CSI Class 1-5 according to the below scheme:

  • CSI Class 5: 125-150 points
  • CSI Class 4: 100-124 points
  • CSI Class 3: 75-99 points
  • CSI Class 2: 38-74 points
  • CSI Class 1: 0-37 points

Note that third-party verification of the data is required to obtain rebates on Swedish fairway dues and port fees. Read more about the process under registration & certification.

Data sharing

Ship-owners can not only see the scores of their own vessels online, but can also look at how other shipping companies are performing. Stakeholders such as cargo owners and forwarders use the database to select their sustainable shipping options.