Accurate simulation of two-terminal resistive random access memory (RRAM) behavior is accomplished by solving equations including state variables for filament length growth, filament width growth, and temperature. Such simulations are often run in a SPICE environment. Highly accurate models simulate the dynamic nature of filament propagation and multiple resistive states by using a sub-circuit to represent an RRAM cell. In the sub-circuit, voltages on floating nodes control current output while the voltage dropped across the sub-circuit controls growth and temperature characteristics. Properly executed, such a sub-circuit can accurately model filament growth at all phases of conductance including dynamic switching and a plurality of resistive states.