A mathematical point is only a location, and has no dimensions. Of course, when you mark the point on paper, it has the same diameter as the lead in your pencil, or the ball on your BIC.
a pencil
A pencil is usually sharpened to a point.
If you mean the diameter of a circle with area pi, then the diameter is 2. If you mean the diameter of a circle with circumference pi, then the diameter is 2. If you mean the diameter of a circle with diameter pi, then the diameter is pi. If you mean the diameter of a circle with radius pi, then the diameter is 2pi.
The piece of lead in a pencil or the pencil.
The standard diameter of a pencil is about 0.3 inches or 7.6 millimeters.
The diameter of normal size pencil lead is about 0.7 millimeters.
The number of the pencil is based on the type of carbon lead used inside. The thicker the carbon lead gets the higher the number of the pencil becomes. If you notice a mechanical pencil is 0.9mm in diameter so it would be called a #0.9 pencil. A #2 pencil's lead is 2mm in diameter. So Why would we call a pencil a #3 pencil? Because it's lead is 3mm in diameter.
A standard pencil is typically about 7 millimeters in diameter, which is roughly 0.28 inches.
A typical pencil is about 7 inches long and 0.25 inches in diameter.
A 7mm pencil lead is thicker than a 5mm pencil lead. The diameter of the lead determines its thickness, so the lead with a larger diameter will be thicker.
It is twice its radius
An ordinary pencil is one example.
The diameter of a standard pencil is typically around 0.25 inches or 6.5 millimeters.
Micrometer
Millimeters.
A standard pencil eraser is typically around 1/4 inch in diameter.