Various embodiments of the present disclosure provide a box sealer including a first box measurer including a top flap engager configured to move downwardly from a disengaged position above a box at a box measuring position to an engaged position in which the top flap engager engages one or more of the four upright open top flaps of the box. The amount of movement of the top flap engager is partially used to determine the height of the box. The determined height is then used to position a combined flap closer and flap sealer at an appropriate position.