Embodiments include systems and methods for determining cardiovascular information. A method includes generating an anatomical model of a portion of a patient's vasculature and a computational model of a blood flow characteristic therein； determining a range of uncertainty for an uncertain parameter, clinical variable, and/or geometry of the model； obtaining a probability model comprising statistics for blood flow characteristic calculations, based on the uncertainty value； iteratively modifying the probability model by adjusting the uncertain parameter, clinical variable, and/or geometry using the uncertainty value, to determine statistical variation of the blood flow characteristic with such adjustment； receiving a target confidence level； calculating a blood flow characteristic value and range of variation thereof consistent with the target confidence level, using the computational model and the modified probability model； and outputting the anatomical model, flow characteristic value, and range of variation.
