I'm assuming that you're asking about wheels, not wells.
Basically they're measured straight across the centre, from one edge to the other. What makes things rather confusing is that usually the measurements refer to from one edge of the tire to the other.
But this means that if you use a tire that is thinner than what was originally intended when the size was defined, then your measurement might not make much sense. It's safer to use the I.S.O. method, where you measure to the point of the rim where the tire attaches and gives a more well-defined value in mm. As long as the BSD (bead seat diameter) matches, each rim can take a couple of different tire widths w/o trouble.
Bicycle tires are measured by their diameter in inches. The standard unit of measurement for bicycle tires is inches, with the diameter typically ranging from 12 to 29 inches.
3328.4 inches
Bicycle wheels are accurately measured for size and fit using the diameter of the wheel, typically in inches or millimeters. This measurement is important for ensuring the wheel fits properly within the frame of the bicycle and aligns with the brakes and other components. Riders can also consider factors like width and tire size to ensure a proper fit for their specific needs.
Bicycle gears are measured in inches. The formula is 27 (Size of wheel.) divide by number of teeth on rear sprocket. Multiplied by the number of teeth on chainwheel. Example 27 divide by 18, times 50, equals 75.0 inch gear.
a pencil is measured in inches
inches and on some motors are measured like 0.035 inches
Rainfall is typically measured in millimeters (mm) or inches (in).
Inches is measured by inch-tape.It is also measured by scale.
12 inches
Inches
Area of bicycle wheel: pi*13 squared = 169*pi or about 531 square inches
Inches