Summary | The SAC/FEMA probabilistic framework is based on a pioneering closed-form expression to analytically estimate the value of the risk integral convolving seismic hazard and structural response. Despite its immense practicality, implementation has been hindered by reduced accuracy due to a number of approximations needed to achieve a simple form, the most significant being the power-law approximation of the seismic hazard curve. To mitigate this problem, two approaches are hereby offered, namely (a) selecting an appropriately-biased power-law fit and (b) offering a novel closed-form expression involving a higher order approximation. Where blind application of the original format could involve error in excess of 100% for the predicted mean annual frequency of limit-state exceedance, biased fitting reduces it to less than 25% while for the new closed-form it remains consistently below 10%. Although other sources of error still remain, the robustness achieved opens new avenues of application for this popular format.