How do I calculate capillary entry pressure for a given pore width and and a known surface tension?

This is not homework, it is research. I have drops of known mixtures that I drop onto dry samples and I measure the surface tension of the sample this way. I also have data about pore-size distributions on the sample. I can correlate surface tension to pore size but I am also interested in explaining why they correlate in a particular way.

I know that micropores will enhance hydrophobicity (drive up surface tension) because the pores are too small to admit water. I believe this is quantified by capillary entry pressure under a gravity-draining system at atmospheric pressure.

I want to find the pore size that forbids entry by water due to capillary pressure considerations.

Does anyone either:
1) Know how to calculate this?
2) Know what this theory might be called?
3) Have suggestions for another way to determine what size of pore is too small for water to enter it?