Calculations of expected income are therefore based on a number of assumptions in terms of the type of traffic using the link and the price level.

The first important premise deals with the number of vehicles using the road connection. The most recent traffic prognosis from 2003 suggests that 9,150 cars will use the link per day. Since then, the opening date has been moved to 2018 and the prognosis therefore shows a moderate projected growth of 1.7 percent, resulting in a daily traffic of 9,600 vehicles per day. However, this figure has been reduced by 20 percent, as there will be a certain adjustment period, while the market gets used to the existence of the new traffic corridor. Calculations are therefore based on a figure of 7,700 vehicles per day, when the link is expected to open in 2018 (also see Traffic forecasts).

Another important premise is the price each vehicle should pay to use the road link. Financial calculations for the fixed link are based on the ticket price of the Rødby-Puttgarden ferry route in 2002, allowing for inflation. In 2008, a single fare for a car was 54 Euro (ca. DKK 400).

A third important premise is the income generated from passenger trains using the rail link. This has been estimated as being 47 million Euro per year (ca. DKK 350 Million). This amount corresponds to the amount the rail companies will save using Fehmarnbelt, which is 160 km shorter than the existing route over the Great Belt.