The transverse size of a human adult eye is approximately 24.2 mm and the sagittal size is 23.7 mm.
This chart shows the diameter of eyes for various animal species and then the size of the eyeball at different scales. The measurements are for the total diameter of the eyeball not the iris. I'll hopefully have some resources on irises and pupils at a later time.  No, cells arent all the same size. The size of a cell depends on the organism it belongs to and its function, for example a bacterial cell would be a maximum of around 10micro … ns whereas an average human cell is between 10 and 100 microns, with size varying as I said dependant on function. 5 people found this useful. Answer   The average human brain weighs three pounds (1.36 kilograms). The average female brain capacity is 79.3 cubic inches, slightly smaller than the male … brain of 88.5 cubic inches. The largest human brains may be twice those of average size, but size has no relevance to brain performance. Answer   the average forehead size of a human is roughly between 6 and 10 centimetres though this can vary widely. If someone has a large forehead it does not necessarily … mean they have a large head overall, sometimes it means that their hairline is further up their head. It can easily be calculated using the human eye’s focal length (~22mm) and physical aperture size. Here’s what Wikipedia has to say: Computing the f-number of the human eye involves computing the physical aperture and focal length of the eye. The pupil can be as large as 6–7 mm wide open, which translates into the maximum physical aperture. The f-number of the human eye varies from about f/8.3 in a very brightly lit place to about f/2.1 in the dark. The eyeball grows rapidly, increasing to 22.5–23 mm (approx. 0.89 in) by three years of age. By age 13, the eye attains its full size. The typical adult eye has an anterior to posterior diameter of 24 millimetres, a volume of six cubic centimetres (0.4 cu. in.), and a mass of 7.5 grams (weight of 0.25 oz.). Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors. The vertical measure, generally less than the horizontal distance, is about 24 mm among adults, at birth about 16–17 millimetres (about 0.65 inch). The transverse size of a human adult eye is approximately 24.2 mm and the sagittal size is 23.7 mm with no significant difference between sexes and age groups. Strong correlation was found between the transverse diameter and the width of the orbit (r = 0.88). Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors. The average size of a human cell varies quite a lot. a single nerve cell can be up to a meter long while a cheek cell averages about 50 micrometers or .05 mm. the average cell … though is between 10 micrometers and 100 micrometers. 29 people found this useful. Answer   the average forehead size of a human is roughly between 6 and 10 centimetres though this can vary widely. If someone has a large forehead it does not necessarily … mean they have a large head overall, sometimes it means that their hairline is further up their head. How the Human Eye Works. The human eye can be compared to a camera which gathers, focuses, and transmits light through a lens to create an image of the environment. In a camera, the image is created on film; in the eye, the image is created on the retina, a thin layer of light sensitive cells at the back of the eye.  The eye continues to grow, gradually, to a length of about 24-25 millimeters, or about 1 inch, in adulthood. A ping-pong ball is about 1 inch in diameter, which makes the average adult eyeball about 2/3 the size of a ping-pong ball. 
http://www.noadi.net/EyeSizes.html http://www.answers.com/Q/Are_all_human_eyeballs_the_same_size http://www.answers.com/Q/What_is_the_average_size_of_human_eyeball http://petapixel.com/2012/06/11/whats-the-f-number-of-the-human-eye/ https://en.wikipedia.org/wiki/Human_eye https://en.wikipedia.org/wiki/Human_eye http://www.answers.com/Q/What_is_the_average_size_of_human_eyeball http://www.afb.org/info/the-human-eye-its-functions-and-visual-impairment/5 http://www.tedmontgomery.com/the_eye/
what size is the human eyeball