Many risk factors for disease are suggested as screening tests when there is little prospect that they could be useful in predicting disease. To avoid this, it is useful to know the relationship between the relative risk of a disease or disorder in people with high and low values of a risk factor, and the equivalent screening performance in terms of the detection rate (sensitivity) for a specified false-positive rate. We describe an interactive Risk-Screening Converter, accessible from the Internet (http://www.wolfson.qmul.ac.uk/rsc/), that transforms an odds ratio into the equivalent estimates of detection and false-positive rates. The converter is intended for general clinicians, for people engaged in research into risk factors and disease, and for those who give advice on applying such research findings into medical practice. It should help to distinguish effective screening methods from ineffective ones, and so improve clinical guidelines relating to screening and the prediction and prevention of disease.