I present a compact physics-based model of the drain current, charge and capacitance of graphene field-effect transistors, of relevance for exploration of DC, AC and transient behavior of graphene based circuits. The physical framework is a field-effect model and drift-diffusion carrier transport incorporating saturation velocity effects. First, an explicit model has been derived for the drain current. Using it as a basis, explicit closed-form expressions for the charge and capacitances based on the Ward-Dutton partition scheme, covering continuosly all operation regions. The model is of special interest for analog and radio-frequency applications where bandgap engineering of graphene could be not needed.