Indoor mold exposures have been qualitatively linked to asthma for more than 25 years. Our goal has been to turn this qualitative link into a quantitative assessment of asthma risk from mold exposures as estimated by the home’s environmental relative moldiness index (ERMI) value. The home’s ERMI value is derived from the quantitative PCR analysis of 36 molds in a dust sample. Six epidemiological studies of the relationship between ERMI values and asthma, in cities across the U.S., showed that both children and adults with asthma were living in homes with significantly higher ERMI values than the control or comparison homes. Based on these six studies, the accuracy of the ERMI value’s link to occupant asthma was analyzed using receiver operating characteristic (ROC) curve and area under the curve (AUC) statistical analysis. The AUC was 0.69 which places the test accuracy in the “fair to good” range for a medical diagnostic test. A logistic regression analysis of the six studies was performed to generate an equation that can be used to predict occupant asthma at specific ERMI values. The ERMI metric may be a useful tool to link the quantification of mold contamination in U.S. homes to some asthma health effects.