The Mi Smart Band 4 lasts up to 20 days on a single charge according to Huami Laboratory testing. Tested using default settings with 30-minute automatic heart rate monitoring enabled, receiving 100 notifications per day, 2 alarms per day, vibrating for 5 minutes, touching the touch button 10 times per day, and syncing with the app once per day. Actual results may differ due to differences in environment, use, and settings.
Water-resistant up to 50m. Water-resistance is in accordance with GB/T 30106-2013 standard. Testing performed by the National Quality Supervision and Inspection Center for Watches. Mi Smart Band 4 water resistance report code: QT1902005; The 39.9% larger display size” is in comparison to Mi Band 3. Mi Band 3’s display measures 17.26mm in length and 9.66mm in width. Mi Smart Band 4 measures 21.6mm in length and 10.8mm in width. Also Calculated as (10.8*21.6-9.66*17.26) / (9.66*17.26), the Mi Smart Band 4’s display is 39.9% larger than Mi Band 3’s display.