In this paper, an approximate and quick estimation model is proposed based on engineering oriented methodology to support the existing bidding practice which consumed more time due to Material Take Off (MTO) preparation. The cost estimation model is based on standard quantity of structural steel for superstructure/topside which calculated from the mean value of respective steel section and strength classification. 44 offshore structures were collected and analysed for model development and 5 for model verification. 7 steel sections consist of plate, welded tubular, seamless tubular, beam, miscellaneous steel, grating and stair tread with respective strength classification such that High Strength, Through Thickness Properties (TTP) and Mild Strength steel were identified that accounted for overall structural steel costs. The completed cost estimation model were validated through inter-rater agreement between Subject Matter Expert (SME) in the field and verified by comparing the estimated cost calculated by the model and the actual bidding cost. The result showed that the model yield an error range less than +8% and can be considered acceptable in construction of fixed offshore structure.