A measuring device and method for simultaneously measuring both a slice lip opening and a setback of a headbox slice in a headbox of a papermaking machine are provided. The measuring device is formed by a block having a stop depending from the bottom at the back of the block that is adapted to be placed against the apron lip tip. A height measurement scale is located on a side surface and extends in a direction from the front to the back adapted for measuring the slice opening b. A setback distance measurement scale is located at the top extending from a zero position aligned in a fixed relation with the stop surface toward a front of the block for measuring the setback L. A movable sliding indicator connected to the block slides includes a slice lip locator adapted to move into sliding contact with the slice lip to indicate the setback distance L on the setback distance measuring scale while simultaneously indicating the slice opening b on the height measurement scale.