We are trying to develop a standard mass-radius relationship for exoplanets to predict the most likely value from the other. There are very high uncertainties in predicting radius from mass but we just need a reference relation. Here we created a simple empirical formulation combining solar and extrasolar planets data. The relation assumes that any body below one Earth mass is rocky in composition, those between 1 to 200 Earth masses start as rocky but move quickly to oceanic and gas giants, and those above 200 Earth masses are gas giants (Figure 1 and 2). The relation is give by:
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