This paper presents a SPICE compatible model of a dual-gate bilayer graphene field-effect transistor. The model describes the functionality of the transistor in all the regions of operation for both hole and electron conduction. We present closed-form analytical equations that define the boundary points between the regions to ensure Jacobian continuity for efficient circuit simulator implementation. A saturation displacement current is proposed to model the drain current when the channel becomes ambipolar. The model proposes a quantum capacitance that varies with the surface potential. The model has been implemented in Berkeley SPICE-3, and it shows a good agreement against experimental data with the normalized root-mean-square error less than 10%.