There is actually no specific score that is considered the highest IQ possible. There are a number of different IQ tests, and each of them has its own scoring method. However, an IQ of over 180 is considered profoundly gifted, and an IQ of over 200 is considered immeasurable genius.
Most IQ tests are represented on a bell curve. The scores for a particular group are plotted on a graph and often resemble the shape of a bell. The peak of the bell, or the highest point, is where the majority of the test takers land. One side of the bell represents lower than average, while the other side represents higher than average.