We expanded our analytical compact model for the drain current of undoped or lightly doped nanoscale FinFETs, in order to predict and decompose variability in the electrical characteristics of FinFETs. The model has been evaluated by comparison to TCAD simulated devices with predefined variability. Successful application to experimental data of FinFETs with fin width W_fin= 15 nm, gate length L_G =30 nm, equivalent gate oxide thickness t_ox = 1.7 nm and fin height H_fin= 65 nm, has attributed their behavior to geometrical variations (of L_G, W_fin) and variability in the metal gate work function (Φ_m). Furthermore, variability of FinFETs having different number of fins (2-50) and fin's pitch (200-1000 nm) has been investigated.