What is a zero error and why does it matter for my caliper measurements? The zero error on a caliper has to do with the baseline point of the caliper. If properly cleaned and closed, a caliper ought to measure 0.00 exactly. Occasionally, this will not be the case and then you have a zero error. A zero error on a caliper can be positive or negative in direction. A positive zero error occurs when the caliper jaws are closed, but the readout has some positive value, whereas a negative zero error occurs when the caliper jaws are closed, but the readout has some negative value. This can occur when a caliper is not properly maintained, or after normal wear and tear from use. No matter the cause, a zero error occurs when the caliper is not properly calibrated to the zero point. Knowing if your caliper has a zero error is extremely important for the accuracy of your measurement. If there is any discrepancy in the calibration of your caliper, you must then account for it in your final measurement.