A compact model for dual-gate (DG) carbon-nanotube field-effect transistors (FETs) (CNTFETs) is presented. This compact model includes the most significant mechanisms present in DG CNTFETs such as the Schottky barrier at the metalnanotube interface, charge and electrostatic modeling, the band-to-band tunneling effect, and quasi-ballistic transport through the Landauer equation. Also, the structure of our DG CNTFET model and its associated equations are versatile and can be used to model different kinds of 1-D ballistic DG FETs, such as graphene-nanoribbon-based devices. Furthermore, this compact model is compared with measurements from two different technologies. Finally, a simple ring oscillator circuit has been simulated using ten identical devices.