Electronic sphygmomanometers and mercury sphygmomanometers are accurate after proper calibration and in accordance with international standards. Mercury sphygmomanometers are commonly used in China, especially in hospitals, and electronic sphygmomanometers are commonly used abroad. Patients with mercury sphygmomanometers are more assured that manual measurement is more accurate, but manual measurement may vary slightly depending on the tester, and the disadvantage is that it contains mercury and is polluting to the environment. Electronic sphygmomanometers are calibrated and have accurate values. The key is to test in the correct posture and to measure three times under different conditions and take the average, which is more accurate. Electronic sphygmomanometer in the regular hospital by the equipment department calibration, ordinary patients can go to the hospital, with manual or calibrated hospital electronic blood pressure meter measurement, and self-measurement values for comparison, if the difference between the two is not large, suggesting that the blood pressure meter is accurate; otherwise, the need for professional maintenance.