38 mm = 3.8 cm
A 7 mm diameter circle is the equivalent of a circle with a 0.275-inch diameter.
The answer is about 2.9mm at 80x.
circumference = diameter X pi diameter = circumference/pi diameter = 55 mm/3.1416 diameter = 17.5 mm
If the entire field of view is 32 mm and the object occupies 25% of that then you will multiply 32 by 0.25. The result is 8 mm.
The circumference of a circle with a diameter of 110 mm is 345.58 mm
The diameter of a circle that has a circumference of 113 mm is about 35.97 mm
The circumference of a circle with a diameter of 55 mm is: 172.8 mm
The circumference of a circle with a diameter of 13 mm is: 40.84 mm
The circumference of a circle that is 16 mm in diameter is 50.27 mm
Diameter 17.91 mm (0.705 in) It is 17.91 mm (0.705 in) in diameter