A properly calibrated load-cell is critical for the safe operation of a rod-pumping system. Load readings are utilized for shutdown thresholds, and incorrect measurements can cause those safe load limits to be exceeded. Correct surface load, combined with position measurement, is also important for the diagnosis of the complete pumping system. The diagnostic method for calculating down-hole conditions presents an interesting opportunity to validate surface load measurements, even from the incorrect load measurements themselves. The calculated down-hole dynamometer card will be transposed on a distinct diagonal with respect to both load and position, if the input surface load measurements are incorrect. A load offset can then be identified from this shifting and the surface load measurements can be corrected. Calculated pump cards have been traditionally aligned with the surface dyno card position, and so this diagonal pump card shifting correlation with incorrect, or unexpected, surface load has not been realized.