  We have measured the spin splitting in single-layer and bilayer graphene by
means of tilted magnetic field experiments. Applying the Lifshitz-Kosevich
formula for the spin-induced decrease of the Shubnikov de Haas amplitudes with
increasing tilt angle we directly determine the product between the carrier
cyclotron mass m* and the effective g-factor g* as a function of the charge
carrier concentration. Using the cyclotron mass for a single-layer and a
bilayer graphene we find an enhanced g-factor g* = 2.7 \pm 0.2 for both
systems.
