Matthias Hildesheimer’s age was derived from the Strongest Sage Fandom. The fandom says that he is currently 12 years old and that he was 6 years old during his debut in the novel.
There is no official height for Matthias Hildesheimer. We estimated his height with the help of Hikaku Sitatter, by observing the scale difference between his sword and his height. This can be seen in the “appearance section” on his character profile in the Strongest Sage Fandom. We used the “Light Novel Design” for the comparison. If we make his sword sit straight from his feet up, it would have a maximum height equivalent to Matthias’s waist height level. According to Wikipedia, historical one handed swords would usually have a length between 45 to 80 centimetres. For this comparison, we used 80 centimetres since if we use anything lower, it will not correlate with the lowest average height (137 cm) for a 12 year old boy mentioned on Children SWI. If this evaluation is correct, then it would mean that Matthias should have at least a minimum height of 137cm and a maximum possible height of 150cm. For this estimate, we will take the midpoint of 137cm and 150cm, it should be somewhere around 143cm. To conclude, Matthias’ estimated height is around 4 feet and 8 inches.