How can I tell if it's worth adding Farms

So I’ve reached the a Max population and my colony is no longer growing. How an I tell if I’m being capped by planet size (and % land) or simply the number of farms needed to sustain my population? I.e. how can I tell if it still makes sense to build more farms?
Here is the info I’m given:

For people’s realm the calculation is:

Planet Size X Landmass X 0.75

That is the Max population for that planet, farms are required to support that population however, and each planet as an inherent value for which in can support.

So lets say you take a planet, and your population max says 31,000, that isn’t actually the Max of the planet, but the Max it can support. Every farm will add 25,000 to that support level.

You have to use the above calculation to see the full max pop that the planet can have.

Thank you Cheatle!
It would be good if the UI could make things a bit clearer, I don’t really want to ALT+Tab to a calculator for each planet.

Me again. Just checking the calculation using the below screenshot.
So 22,498[planet size] * 50 [Land mass] * 0.75 = 843,675
Did I do this right? e.g. 50% land mass should be ‘50’ and not ‘0.5’ or something in the calculation?

Your working out looks right to me.

This is exactly the reason I was posting about more detail on planets earlier Scientific Survey - Planetary Prospecting

Its confusing and reading the Wiki/old guides isnt going to help as the reworked the metrics for Alpha 3. If we had a nice clear line of text somewhere (anywhere!) that said this…!

The irony was that until the first patch of A3 they did indeed have the max pop possible on each planet. But that was deleted in an effort to fix a pretty hairy population bug they had?

They need to have four lines of text:

Current Population: This is your current pop
Planet Supported Population: This is how much the planet can support without farms
Supported Population: This is the total with farms and planet support
Max Population: This is the max of the planet