A method for estimating extracorporeal blood volume in at least a portion of a fluid canister. A light source may be activated, and an image of the fluid canister is captured with an optical sensor. The image may be a color frame of a video stream. A color-related feature is extracted from at least a portion of the image. A concentration of hemoglobin is estimated based on the extracted color-related feature. A fluid level of fluid within the fluid canister may be estimated from the image. Extracorporeal blood volume based on the estimated concentration of hemoglobin and a fluid volume or the estimated fluid level. The estimated extracorporeal blood volume is displayed on a display. The estimated extracorporeal blood volume and the estimated fluid level may be monitored over time. The optical sensor may be disposed on a handheld mobile device mounted to a side of the fluid canister.