Disclosed are embodiments for modeling contact resistance of devices, such as metal oxide semiconductor field effect transistors or varactors, that specifically have a multi-finger gate structure. In the embodiments, a set of expressions for total contact resistance are presented, in which (i) the total contact resistance is the sum of the resistance contribution from the contact (or the set of all contacts) in each diffusion region, (ii) the resistance contribution from the contact (or the set of all contacts) to the total contact resistance is the product of its resistance and the square of the relative electric current passing through it, and (iii) the electric current passing through the contact (or the set of all contacts) in a shared diffusion region (i.e., in an inner diffusion region) is twice of the electric current passing through the contact (or the set of all contacts) in an unshared diffusion region (i.e., in an outer diffusion region).