Workfunction of graphene/TiN stack is estimated using a metal oxide semiconductor (MOS) test structure. A thickness series in SiO2 is used to exclude the contribution of fixed oxide charges and interface states to the flat band voltage. Workfunction of thick multilayer graphene sheets (∼ 7nm) is obtained as 5.04 eV. Incorporation of graphene in the gate stack of MOS structure is seen to result in negligible contribution of charges to flatband voltage. This implies that flatband shift can be used for estimating the work function with reasonable accuracy, especially if SiO2 in the thickness range of 3 - 4 nm is used. © 2012 IEEE.