Why isn't standard Gibbs free energy always zero? I read in my textbook that one of the standard conditions we should use when calculating the standard Gibbs free energy is having a concentration of 1 M of all the reagents and the products in the reaction. But if you use the formula $G = -RT\ln K_\mathrm e$ and you use 1 M to calculate it, you would always get zero.

So that means 1 M would be the initial concentration of reagents and products before reaching equilibrium?
$\Delta G = \Delta G^\circ - RT \ln(K)$

It isn't directly $G$, but formula for change in free energy. Also, in standard conditions $\Delta G = \Delta G^\circ$, so it isn't necessarily 0.

Relevant reading on a website