A general methodology to evaluate vulnerability functions suitable for a probabilistic global risk assessment is proposed. The methodology is partially based in the methodological approach of the Multi-hazard Loss Estimation Methodology (Hazus) developed by the Federal Emergency Management Agency (FEMA). The vulnerability assessment process considers the resolution, information and limitations established for both the hazard and exposure models adopted. Seismic and wind vulnerability functions are estimated for each one of the building classes defined in typical global exposure databases. They consider possible variations according to the design level in different regions of the world which accounts for variations of the expected quality of construction and the design code compliance level. In addition, a consistent, expert opinion based methodology is proposed in order to assign particular vulnerability functions to building classes according to the development level of each country, the city complexity and the hazard level of the region. The proposed set of vulnerability functions and the assignment procedure were used for the probabilistic global risk assessment made in the framework of the UNISDR’s Global Assessment Report on Disaster Risk Reduction, GAR 2013. Recommendations for the refinement of the methodological approach are included for future global or scaled regional risk assessments.