Number of primes $p$ less than $n$ s.t $p \equiv 3 \pmod 4$

Question

I would like to find a lower and upper bound for the number of primes less than $n$ that are $3\pmod 4$. My guess is that it should be close to half of $\pi (n)$ but cannot find a proof or generate myself. Is there a way to prove some lower and upper bounds as we have for $\pi (n)$?

Thanks