Why is tolerance important when using gage blocks? Knowing the tolerance of your gage blocks, or their grade, is an important tool to simplify the process of using them. Essentially, the tolerance is a way in which to classify how accurate your gage blocks will be. When calibrating a fixed gage, you might normally need to know the tolerance to stay within the required accuracy. The grade, or tolerance level, of your set of gage blocks helps to standardize this process and ensure that the µm is where you need it to be in order to perform the calibration. This eliminates the need to calibrate the length of the block stack from the calibration report. Various grades, or tolerances, are used for various calibration and precision measurement purposes, but as long as you know the tolerance of your gage blocks, you are at an advantage.