To calibrate your Leica Disto, you first want to establish a consistent baseline. It should be something that’s easy to get to (such as a window frame or the length of a room that’s between one and ten meters away from you), and determine its length with a tape measure. Take at least ten measurements with the Leica Disto, and record each one. Average the values to find out if there are any deviations from your baseline, and make the appropriate adjustments.