In Laser Powder Bed Fusion (LPBF), knowledge of the melt pool geometry is an important factor avoiding the formation of defects, such as lack-of-fusion or keyhole porosity. While common energy density definitions allow a relation between melt pool dimensions and processing parameters, their usefulness has limitations regarding comparability of different materials. Dimensionless numbers, including physical material properties, can be used to overcome this disadvantage. In this study, two dimensionless numbers, namely dimensionless enthalpy and Peclet number are introduced and proposed to predict melt pool dimensions independent of material. Dimensionless enthalpy defines a ratio of laser energy input to the material to energy needed for melting of the same and, thereby, characterizes the energy input. However, it does not account for heat loss during the interaction and, therefore, the Peclet number, being the ratio of heat convection to conduction, is also studied in this presentation. Single scan track dimensions were evaluated for five different alloys (In718, 316L, Ti6Al4V, M300, AlSi10Mg). A variation in the relation of melt pool dimensions with Peclet number was noticed and is attributed to changes in heat distribution mechanisms. Despite different physical properties of the investigated alloys, relations collapsed into single trend lines for melt pool width and depth taking the Peclet number into account. For samples in keyhole mode predictions achieved acceptable error levels. Thus, the two introduced dimensionless numbers enable estimation of melt pool dimensions with a simple spreadsheet calculation.