In the relationship between 'DeltaG' and K for a given reaction, if 'DeltaG' is negative, what is K?

Consider a hypothetical reaction:

A ↔ B

The change in free energy, ΔG can be related to the equilibrium constant K as:

ΔG = - RT ln K

i. e. K = exp (-ΔG/RT)

When ΔG is negative, the exponential becomes positive which results in a high value of the equilibrium constant (K). More and more of the reactants get converted into products and the reaction tends to be spontaneous.