A cell processing system includes a processor connectable to a source container filled with a biological fluid and one or more wash media containers. The processor includes a separator connectable to the source container and a product container, the separator configured to separate the biological fluid from the source container into at least two streams. In addition, a controller is coupled to the processor and configured to: cause the separator to separate the biological fluid into at least two streams, direct one of the at least two streams into the product container, subsequently pause processing of the biological fluid, after pausing, determine a measured cell count in the product container, and add fluid to the product container from the wash media containers as a function of the measured cell count in the product container while the product container is connected to the wash media containers.
