We prove that for each γ ∈ (0, 2), there is an exponent d γ > 2, the "fractal dimension of γ-Liouville quantum gravity (LQG)", which describes the ball volume growth exponent for certain random planar maps in the γ-LQG universality class, the exponent for the Liouville heat kernel, and exponents for various continuum approximations of γ-LQG distances such as Liouville graph distance and Liouville first passage percolation. We also show that d γ is a continuous, strictly increasing function of γ and prove upper and lower bounds for d γ which in some cases greatly improve on previously known bounds for the aforementioned exponents. For example, for γ = √ 2 (which corresponds to spanning-tree weighted planar maps) our bounds give 3.4641 ≤ d √ 2 ≤ 3.63299 and in the limiting case we get 4.77485 ≤ lim γ→2 − d γ ≤ 4.89898.