Great Ape size:
Common Chimpanzee 4 to 5 feet tall, 88 to 154 pounds. (Average: 4 feet tall and 100 pounds)
Bili Ape: 5 feet to 5 feet 9 inches tall (estimate), 170 to 300 pounds (estimate). (Estimated average: 5 feet 6 inches, 210 pounds)
Bonobo: 3 feet 9 inches to 4 feet 10 inches tall (estimate), 80 to 130 pounds (approx.). (Estimated average: 3 feet 10 inches, 86 pounds)
Orangutan: 4 feet to 5 and a half feet tall, 150 to 350 pounds. (Average: 4 feet 6 inches, 170 pounds)
Western Gorilla: 5 to 6 feet tall, 280 to 540 pounds. (Average: 5 feet and 6 inches, 375 pounds.)
Mountain Gorilla: 5 feet 3 inches to 6 feet 5 inches, approx. 325 to 450 pounds. (Average: 5 feet 7 inches, 375 pounds.)
Grauer's Gorilla: 5 feet 8 inches to 6 feet 7 inches (approx.), 365 to 615 pounds (estimate).
Human: 4 feet 10 inches to 6 feet 4 inches (approx.), 100 to 300 pounds (approx.). (Average: 5 feet 9 inches, 160 pounds)
(Notes: The Bili Ape is not a separate species from chimpanzees. I gave a size estimate for them thought because despite being a population, not species, of chimpanzees, they are quite larger than the average chimpanzee [Perhaps up to three times the size of the average chimpanzee, two times their size on average.], so I thought it would be worth mentioning here.
All three species of Pongo, the orangutans, seems to be the same size, so I did not give sizes for each of them since it would probably be redundant to do so.
To get the average weight of a human, I used a BMI calculator. A healthy weight for 5 feet and 9 inches is approx. 160 pounds.
I do not exactly know the average weight of a Mountain Gorilla. I have seen at least two different averages stated; 332 pounds and 352 pounds. The average weight can be assumed to be 342 pounds. We get that if we add the two weights up and divide them by two. This can be considered the average weight until further information is found about these apes.
Though not included in the sizes, adult male gorillas can perhaps weigh anywhere from 270 pounds minimum, to perhaps 650 pounds maximum. Ngagi the Grauer's Gorilla weighed a whopping 635 pounds when he died at the approximate age of 18. I do not know what he died from, however. It almost certainly isn't heart disease, though. Reason being, he was stated to be "well-proportioned" [Scientific American, June 1943], Even despite the fact that he stood at only 5 feet 8 inches, which is actually below average height for Grauer's Gorillas [Average Height: 6 feet tall]. He was also stated to be "broad of shoulder", though I cannot find the source for that statement. When I do find it, I will cite it here.
Here is the link to an image of a page from Walker's Mammals of the World which states that Ngagi is "broad of shoulder"; https://i.imgur.com/Sa6b3mo.jpg Note that you can click on the image to zoom in on it. The part that I'm talking about is in the top-right corner of the image.
The largest healthy orangutan that I could find a weight for was Juara the orangutan from St. Louis Zoo; https://www.stltoday.com/news/local/metro/orangutan-at-st-louis-zoo-dies/article_98062c06-a4bd-11df-aaeb-0017a4a78c22.html Juara was noted to have been unusually large at a whopping 375 pounds. Gorilla beringei graueri (talk) 20:32, 25 August 2021 (UTC)