Systems, methods, and apparatus are disclosed for determining quantitative hormone and chemical analyte results from qualitative test results. An image is taken of an ovulation test device. The image is analyzed to identify a darkness intensity ratio (T/C ratio) between a darkness value of a test-line to a darkness value of a control-line. Additionally, a quantitative substance level may be determined using the T/C ratio, by identifying the type of test device and referencing a data structure that relates quantitative substance levels to T/C ratios for the identified type of test device.