The need to shift from a fossil fuel based economy towards a more bio-based economy has received a lot of attention in public debates and policy making in recent years. However, there seems to be some inconsistency in how a bio-based economy is defined as well as how to estimate the size of this bio-based economy. The current article shows, using a Bibliometric analysis, that the topic "bio-based economy" does not come up extensively in the literature by mid 2010. Moreover, it seems that estimating the importance of the whole of a bio-based economy (and thereby not only focusing on one type of production or product) for a region or country is quite rare, besides a few examples. Within Flanders, one such study has been executed by order of the Flemish government. The current article suggests a framework that can be used to estimate the size of the bio-based economy in other regions or countries. It is based on several steps, so called critical points related to conceptualization, disaggregation, information and valuation. The critical points depend on who has and who wants the information, what the context is, what kind of data is available and whether the research should be comparable. The authors suggest that by following their proposed steps, a reliable estimate of the size of the bio-based economy can be calculated. (C) 2011 Elsevier Ltd. All rights reserved.