# How to find input to Gamma CDF which gives specific probability

I would like a formula which allows me to input some value for a Gamma distribution random variable, and get back the total probability density up to that point.

In essence, I would like say, a value of 0.05, or 0.95 returned from the Gamma CDF.

How do I know what value for the random variable would give this? It appears non-trivial due to the Gamma function itself. Is there actually a solution?

In Matlab you can use gaminv, in R, you can use qgamma, or in python you can use ppf in scipy.stats.