TITLE: Does the unit of measure matter when you are solving for the diameter of a circumference?
QUESTION [5 upvotes]: I understand that the circumference of an object should be divided by $\pi$ when searching for the diameter. What I  don't understand is what unit of measurement should I use, inches, cm, mm? If I want to find the diameter of a $10$ inches circle I would get the same number I would, were I looking for the diameter of that of a $10$ cm circle?

REPLY [9 votes]: Both the diameter and the circumference are lengths, so it doesn't matter what units you use to measure them, as long as you are consistent: both in cm, or both in in., or both in miles or... .The ratio of circumference to diameter will then be $\pi$. In your example, a circle of circumference 10in is bigger than a circle of circumference 10cm; the diameter of the bigger circle is $10/\pi$ in., so the ratio is $\pi$, and the diameter of the smaller circle is $10/\pi$ cm, so the ratio is also $\pi$.