The present disclosure relates to a handheld, single-piece wear gauge for chains, and more specifically, to a wear gauge with an elongated body carved into segments with markings, varied widths, and varied heights arranged along a guiding back rail. A roller chain wear gauge includes a single-piece body with a measuring end and a handle connected to the measuring end, wherein the measuring end includes a plurality of adjacent and contiguous calibrated segments each having a measuring length, a measuring width, and a measurement marking, and wherein the measuring end defines on one side a back rail formed by an alignment of a first side of each of the calibrated segments and a step function formed by the second side of each of the calibrated segments.