Recently, variable digital filters (VDFs) have become an essential research topic. This paper presents a simple method for the design of infinite impulse response (IIR) VDFs with high tuning accuracy. First, VDFs were created using a state-space model based on a frequency transformation, which requires the inverse matrix and the square root that leads to high computational cost. Then a new algorithm was implemented to generate the same VDFs absent the complex calculations that utilized negative binomial and Taylor series approximations in a simple state-space formulation. This algorithm provides high-accuracy approximations of the inverse matrix and square root compared to other algorithms that have been developed. Thus, the proposed VDFs have high tuning accuracy with respect to finite wordlength effects.