A peristaltic pump includes a cam shaft, a plunger-cam follower, a tube receiver, a spring-biased plunger, a spring, a position sensor, and a processor. The cam shaft has a plunger cam. The plunger-cam follower engages the plunger cam to follow the plunger cam and to disengage from the plunger cam. The spring-biased plunger is coupled to the plunger-cam follower and the spring biases the spring-biased plunger toward the tube receiver. The position sensor determines a position of the spring-biased plunger when the plunger-cam follower is disengaged from the plunger cam and the spring applies a force from the spring-biased plunger against the tube. The processor estimates fluid flow utilizing the position of the spring-biased plunger as indicated by the position sensor when the plunger-cam follower is disengaged from the plunger cam and the spring applies the force from the spring-biased plunger against the tube.