The Smart Scale II comes pre-calibrated and ready to use.  For home use customers, calibration should be performed once a year or even less frequently. Since coffee shops will likely be weighing over 50% capacity many times a day, the scales should be calibrated quarterly, or even monthly.
Calibration frequency will depend on a number of variables so everyone's experience will vary. Some of the primary factors for determining the calibration interval are:
• How often the scale is used each day
• How often the scale is used over 50% capacity
• How critical the measurements are (how much error is permissible)
• How well the scale is maintained and stored