We prove a quantitative unique continuation principle for Schrödinger operators $H=-Δ+V$ on $\mathrm{L}^2(Ω)$, where $Ω$ is an open subset of $\mathbb{R}^d$ and $V$ is a singular potential: $V \in \mathrm{L}^\infty(Ω) + \mathrm{L}^p(Ω)$. As an application, we derive a unique continuation principle for spectral projections of Schrödinger operators with singular potentials.