1 milliliter is equivalent to 1 cubic centimeter. The ratio is equal, so it is a direct conversion. This means the number of cubic centimeters is equal to the same number of milliliters.
Centimeters and milliliters are both components of the metric system. The metric system is the choice of most of the countries in the world with the exception of the United States, Liberia and Myanmar. The basic units of measurement in the metric system are meters, liters and kilograms. It is a decimal based system and is expressed in units of ten. The developers of the metric system sought to associate it with items found easily in nature. For example, a meter is one ten-millionth of the distance between the Equator and the North Pole.
Even though milliliters and centimeters are both from the same system, there cannot be a direct conversion. Centimeters measure length and milliliters measure volume. To do an equivalent conversion, one must use cubic centimeters instead. A cubic centimeter is defined as the volume equivalent to a cube of 1 centimeter by 1 centimeter by 1 centimeter. One gram is equivalent to the weight of 1 cubic centimeter of water, which is equal to 1 milliliter. There is no conversion formula, since the ratio is equal.