Data precision for rainfall intensity and runoff rate using tipping bucket technology is controlled by the bucket volume, V, the catchment area, A, and the sampling interval, t. The maximum absolute error is less than V(A.t)-1 and the standard error is given by V(v _ 6 A.t)-1, both of which are independent of the magnitude of rainfall intensity and runoff rate being measured. Therefore, the relative error can be quite large during events with low rainfall intensity or runoff rate. The magnitude of the sampling error given above can be used to assist in experiment and equipment design and in data analysis.