Abstract: The novel umpire tool generally comprises a plate of durable material, the plate defining a hole therethrough. The umpire tool can be used for determining a bat's diameter in relation to an upper limit, typically set by a governing association or rule promulgator. Therefore the diameter of the hole defined within the durable plate is closely sized to the upper limit. A plate brush may be integrally provided so that the umpire tool can also be used to clean home plate. Similarly, a scraper may be integrally provided to clean mud and the like from home plate. Further, an insert may be provided for reducing the diameter of the hole and for measuring a bat's diameter in relation to a second different upper limit.