A work machine includes a prime mover, a hydraulic pump to be operated by the prime mover to output an operation fluid, a hydraulic device to be operated by the operation fluid, a measurement sensor to measure a first temperature and a second temperature, the first temperature being a temperature of the operation fluid at starting of the prime mover, the second temperature being a temperature of the operation fluid after the starting of the prime mover, and a controller including a determiner to determine an upper limit revolution speed based on the first temperature, the upper limit revolution speed being an upper limit of a revolution speed of the prime mover, and a changer to change the upper limit revolution speed based on the second temperature.