Exposure rate is the amount of ionizing radiation per hour in a person’s vicinity (measured in milliRoentgen per hour, mR/h), whereas dose rate is the biological effect on the body from exposure to that radiation (measured in nanoSieverts per hour, nSv/h). As an approximation, a radiological dose rate of 1 mR/h is roughly equal to an exposure rate of 10,000 nSv/h.
For more information about typical exposures and dose rates, visit About Exposure and Dose Rates or Learn About RadNet.