Sit2StandPy is an open source Python package that uses novel algorithms to first detect Sit-to-Stand transitions from lumbar-mounted accelerometer data, and then provide quantitative metrics assessing the performance of the transitions. A modular framework is employed that would allow for easy modification of parts of the algorithm to suit other specific requirements, while still keeping core elements of the algorithm intact. As gyroscopes impose a significant detriment to battery life due to power consumption, Sit2StandPy’s use of acceleration only allows for a single sensor to collect days worth of analyzable data.