We use Minkowski content (i.e., natural parametrization) of SLE to construct several types of SLE$_κ$ loop measures for $κ\in(0,8)$. First, we construct rooted SLE$_κ$ loop measures in the Riemann sphere $\widehat{\mathbb C}$, which satisfy Möbius covariance, conformal Markov property, reversibility, and space-time homogeneity, when the loop is parametrized by its $(1+\frac κ8)$-dimensional Minkowski content. Second, by integrating rooted SLE$_κ$ loop measures, we construct the unrooted SLE$_κ$ loop measure in $\widehat{\mathbb C}$, which satisfies Möbius invariance and reversibility. Third, we extend the SLE$_κ$ loop measures from $\widehat{\mathbb C}$ to subdomains of $\widehat{\mathbb C}$ and to two types of Riemann surfaces using Brownian loop measures, and obtain conformal invariance or covariance of these measures. Finally, using a similar approach, we construct SLE$_κ$ bubble measures in simply/multiply connected domains rooted at a boundary point. The SLE$_κ$ loop measures for $κ\in(0,4]$ give examples of Malliavin-Kontsevich-Suhov loop measures for all $c\le 1$. The space-time homogeneity of rooted SLE$_κ$ loop measures in $\widehat{\mathbb C}$ answers a question raised by Greg Lawler.