[1] He is best known for formulating the Titius–Bode law, and for using this rule to predict the existence of a celestial object at 2.8 AU from the sun which led to the 1801 discovery of what we now know as Ceres.

He drew up the law in 1766, when he inserted his mathematical observation on planetary distances into a German translation of Charles Bonnet's book Contemplation de la Nature.

[2][3] Titius published a number of works on other areas in physics, such as a set of conditions and rules for performing experiments, and he was particularly focused in thermometry.

In his treatises on both theoretical and experimental physics, he incorporated the findings of other scientists, such as the descriptions of experiments written by Georg Wolfgang Kraft in 1738.

Lehrbegriff der Naturgeschichte Zum ersten Unterrichte, his most extensive publication in biology, was on systematic classification of plants, animals, and minerals, as well as the elemental substances ether, fire, air, water and earth.