Abstract: A system for measuring the correct size of the shoes is formed by a sensor (1) located at the frontal tip of the shoe, at the level of the big toe or the longer toe of the foot, so that when the toe touches the sensor, it turns on a preferably bright signal consisting of a led (2). In this way, it will be possible in any moment to verify if the size of the shoe is correct, which is particularly important for children who hardly say when the shoe does no more fit the size of the foot.