A floor panel for forming a floor covering wherein the floor panel is substantially realized on the basis of synthetic material. The floor panel is rectangular and comprises a first pair of opposite edges and a second pair of opposite edges such that both pairs of opposite edges comprise coupling parts allowing for mutually coupling a plurality of such floor panels to each other. The coupling parts of at least the first pair of opposite edges are configured such that two of such panels can be coupled to each other at these edges by means of a turning movement and the coupling parts to this aim consist of a tongue and a groove as well as locking parts, which, in the coupled condition, prevent the shifting apart of tongue and groove. The floor panel has a global thickness which is smaller than or equal to 4.5 millimeters.