The percent error formula is a valuable tool used to calculate the gap between a measured value and the true value. It is represented as the absolute difference between the measured and the actual value, divided by the actual value, and then multiplied by 100. This formula is crucial as it enables us to determine how close or far a measured value is to the actual value. It's important to note that measurement tools may have a margin of error, thus they cannot be considered entirely accurate. Therefore, the percent error formula helps us understand the extent of this error.