Abstract: Monitoring vital signs via machine learning is provided. A system can identify data points of signals detected via skin of a user by an optical sensor that indicate changes in volume of blood flowing through a capillary at the skin. The system generates features from the data points. The system inputs the features into a model to produce output. The model can be trained using training data including features and labels corresponding to blood pressure measurements from a reference device. The system determines a value of blood pressure for the user based on the output from the model. The system provides an indication of the value of blood pressure via an interface.