Specifying the time period is important here. We have the most data for the 5th century BCE, the "Athenian Century," so I'll stick to that. There are two main camps for demographic estimates, one on the lower end and one on the higher end. I think there is more weight behind the latter, and they estimate about 60,000 male citizens on the eve of the Peloponnesian war in 431 BCE, and about 200,000 total citizens (including women and kids) at that same time. This includes both the city (astu) and the demes of the Athenian territory, called Attika. These estimates are based on a number of inputs and pieces of evidence, and also reject the notion that Athens had anything close to a 100% citizen participation rate in any typical political action. Older estimates ranged from 20,000 to 40,000 adult male citizens. Note that Athens+Attika almost certainly had the highest population of any Classical Greek city-state--most were much smaller.

Estimates for non-citizen residents are more difficult, but another 100,000 or even 200,00 is theorized (both in the astu and in Attika). That would be about 1 or 0.5 non-citizens for every citizen. The non-citizen population included slaves and also those the Athenians called metoikoi "dwellers alongside," who were either freeborn foreign residents or else freed slaves. They are typically called "metics" in modern scholarship. Freeborn foreigners had to "register" with an official if they dwelled in Athens longer than a set interval, much like modern visas. They had to pay a "metic's tax" (which could be waived as a special privilege) and they were obligated to serve in the military, if required (usually not). They had no political rights and court cases involving them were run separately from citizen courts. They also had to have a citizen representative for them in such proceedings. They could not technically own land in Attika, though they could acquire and move other goods. They could be awarded the right of enktesis by the city, which allowed them to own property. They are often considered a "merchant class" at Athens, though it is more nuanced than that. Under Perikles' citizenship law, they could not produce Athenian citizen offspring, even if they married a citizen.

After the Peloponnesian War, in the 4th century, the total population of Athens is thought to have dropped significantly, and it is also thought that the ratio of metic to citizen dropped. This would track with a general decrease in Athenian prestige and economic clout in the larger Mediterranean. This trend seems to continue into the Hellenistic period of the 3rd-1st centuries BCE, as the city continued to decline in relative importance. For this entire question, however, evidence is sparse and usually challenging to interpret. Everything is expressed in very rough estimates, and keep in mind that we know much more about Athens than any other Greek polis.

See:

Akrigg 2019. Population and Economy in Classical Athens. ​Cambridge.

Blok 2017. Citizenship in Classical Athens. Cambridge.

Hansen 1985. Demography and Democracy: The Number of Athenian Citizens in the Fourth Century BC.