# What measurements must be known in order to find the density of a substance?

Well, by definition...${\rho}_{\text{density"="mass"/"volume}}$
And the quotient ${\rho}_{\text{density"="mass"/"volume}}$ clearly gives us appropriate units of density as $g \cdot m {L}^{-} 1 \equiv g \cdot c {m}^{-} 3$, or (for gases), $g \cdot {L}^{-} 1$.