A method and system for dynamically determining the degree of workload parallelism and to automatically adjust the number of cores (and/or processors) supporting a workload in a portable computing device are described. The method and system includes a parallelism monitor module that monitors the activity of an operating system scheduler and one or more work queues of a multicore processor and/or a plurality of central processing units ("CPUs"). The parallelism monitor may calculate a percentage of parallel work based on a current mode of operation of the multicore processor or a plurality of processors. This percentage of parallel work is then passed to a multiprocessor decision algorithm module. The multiprocessor decision algorithm module determines if the current mode of operation for the multicore processor (or plurality of processors) should be changed based on the calculated percentage of parallel work.