We find optimal (up to constant) bounds for the following measures for the regularity of the Schramm-Loewner evolution (SLE): variation regularity, modulus of continuity, and law of the iterated logarithm. For the latter two we consider the SLE with its natural parametrisation. More precisely, denoting by $d\in(0,2]$ the dimension of the curve, we show the following. 1. The optimal $ψ$-variation is $ψ(x)=x^d(\log\log x^{-1})^{-(d-1)}$ in the sense that $η$ is a.s. of finite $ψ$-variation for this $ψ$ and not for any function decaying more slowly as $x \downarrow 0$. 2. The optimal modulus of continuity is $ω(s) = c\,s^{1/d}(\log s^{-1})^{1-1/d}$, i.e. for some random $c>0$ we have $|η(t)-η(s)| \le ω(t-s)$ a.s., while this does not hold for any function $ω$ decaying faster as $s \downarrow 0$. 3. $\limsup_{t\downarrow 0} |η(t)|\,\big(t^{1/d}(\log\log t^{-1})^{1-1/d}\big)^{-1}$ is a.s. equal to a deterministic constant in $(0,\infty)$. We also show that the natural parametrisation of SLE is given by the fine mesh limit of the $ψ$-variation. As part of our proof, we show that every stochastic process whose increments satisfy a particular moment condition attains a certain variation regularity.