# Number of lines vs length in Frege proofs

What is the relation between the number of lines (or we could say steps) in a Frege style derivation of a propositional tautology, and its length in the number of symbols?

Obviously you can always add junk axioms of wathever length, but assuming an optimal proof $$\pi$$ in $$m$$ lines, for a tautology of length $$n$$, what can we say about the length of $$\pi$$?