To estimate the economic feasibility of floating and bottom-fixed substructures at various offshore sites, a generally applicable calculation tool has been developed. With this 'LCOE calculation tool' it is possible to optimize the design and reduce the costs of deep offshore wind farms, by analyzing key aspects already during the planning and pre-design phase. Hereby the conducted breakdown of the several cost categories assists identifying main cost-drivers prior a final investment decision. Whereas the influence of varying site specific, technological and financial parameters on the cost-effectiveness is investigated in a sensitivity analysis. To validate and enlarge the tool's dataset, the tool was applied to a real floating concept with the aim to compare the cost-effectiveness of floating solutions with their bottom-fixed counterparts.