In water at 298 K the pKb of methylamine is 3.38 and that of ammonia is 4.75…

$K_b = \dfrac{[\text{RNH}_3^+][\text{OH}^-]}{[\text{RNH}_2]}$, $\text{p}K_b = -\log K_b$, and $\text{p}K_a + \text{p}K_b = 14$ at 298 K. For a solution of concentration $c$, $K_b = \dfrac{x^2}{c - x}$ with $x = [\text{OH}^-]$. Then $\text{pOH} = -\log x$ and $\text{pH} = 14 - \text{pOH}$. A smaller $\text{p}K_b$ is a stronger base.