Determining the molar mass of conjugated polymers has proven difficult in many situations using conventional means, and this is often exacerbated in the case of polyelectrolytes. In this paper we report on a new method of determining the molar mass of soluble, light-emitting conjugated polymers by coupling emission-based detection with analytical ultracentrifugation. This method is shown to be capable of recovering accurate molar masses with high sensitivity, without the need for standards, and can also identify aggregation behavior.