Microorganisms are generally sensitive to high concentrations of products that they excrete. Such product inhibition and toxicity effects can significantly be reduced by the integration of fermentations with separation technologies to remove the products continuously. Cost-calculations are required to select the preferred integration method. This paper presents a shortcut calculation method that provides easy interpretable results to assist the reader in making rational design choices. The method distinguishes four main cost categories, being capital and operational expenditure for both fermentation and product recovery. We have applied these cost correlations to the production of three typical bio-based bulk chemicals. The results show the origin of the most significant costs in the investigated integrated bio-processes. The presented method can be used to direct future research efforts and might assist in evaluating the impact of integrated product recovery techniques on total production costs of bio-chemicals. (C) 2010 Elsevier Ltd. All rights reserved.