This paper presents a simple mathematical expression to model the effect of statistical dopant fluctuations on threshold voltage ( $V_{th}$ ) of junction field-effect transistors (JFETs). The random discrete doping (RDD) in the active device area is used to derive an analytical model to compute the standard deviation, $\sigma V_{th,RDD}$ of the $V_{th}$ -distribution for any arbitrary channel doping profiles. The model shows that the $V_{th}$ -variability in JFETs depends on the active device area, channel doping concentration, and the depth of the channel depletion region of the gate/channel $pn$ -junction. The model is applied to compute $\sigma V_{th,RDD}$ for symmetric and asymmetric source/drain double-gate n-channel JFETs. The simulation results show that the model can be used for predicting $V_{th}$ -variability in JFETs.