Ask Larry:

Your Question: What is the difference between a “cc” and “ml”?

Larry’s Response: Well, it’s a long, convoluted story that basically ends with, “that’s the way it is”, or “just because”.

Before comparing and contrasting cc and ml, also be aware that gm can be part of the mix (or “mix up” if you want to consider it that way).

  • cc means cubic centimeter, a measure of volume (one centimeter x one centimeter, x one centimeter is one centimeter to the third power, or one centimeter cubed… cubic centimeter)
  • ml (or mL) mean milliliter (on one-thousandths of a liter), also a measure of volume
  • gm (of Gm) means gram, a unit of weight

The choice to use cc or ml is often dictated by locality and convention. In the metric system it is convention to talk about liquids, for example, in volumes of liters – and parts of liters. People in metric areas will purchase their gasoline in liters and they often report their fuel efficiency as kilometers per liter – while places that do not abide by the metric standards will refer to gasoline in gallons and distance as miles. Those folks report fuel efficiency as miles per gallon. In the final analysis, there is absolutely no difference between a cc and a ml. They are perfectly interchangeable – except for convention. While a person may put a liter of gasoline in their car, they probably wouldn’t call it a cubic decimeter (dm cubed) – even though both represent the same amount.

Hard things are, conversely, usually referred to as cubic centimeters or cubic meters; 1 cubic meters of concrete, for example.

Some definitions mention that a cc and a ml are nearly identical. Let’s just agree that they are identical and use them that way and interchangeably. Basically, use whatever makes you comfortable; cc or ml.

The gm (or Gm) issue complicates things a bit because many of us think that a Gm is the same as a cc, which I’ve just claimed is the same as a ml. This is 100% accurate if we are measuring water at a specific temperature and barometric pressure. The gram is officially defined as the mass 1 cc (ml) of water at 4.5 degrees C at sea level. So it ends up that water has a density of 1gm/cc or 1gm/ml – also referred to as specific gravity.

Temperature and barometric pressure impacts the mass of most things, including water. As temperatures fall and water freezes it will float in liquid water because frozen water has less mass than liquid water. A gram of ice – weighed on a scale at sea level – will contain more volume than a gram of water – but there will be less water in the gram of ice after it melts. However, the difference is very small. Therefore, for all intents and purposes – because we usually deal with items at room temperature – one gram of water is accepted as comparable to a cc and a ml of water even though we know that it isn’t true. The level of error is insignificant.

Not every item presents the same mass per volume as water. Mercury is a heck of a lot heavier than water. One ml or cc of mercury would weigh 13.56 times as much as a similar volume of water. This is all worked out when looking at specific gravity, which is expressed in mass per volume (water is 1, meaning one gram in one cc or ml).

A person who demands absolute accuracy would never equate the volume of a product (cream, gel, liquid, etc) with a simple mass. However, for all intents, a gram of a cream is almost the same as a ml or cc of it. The difference between the specific gravity (sg) of a cream and water is tiny, but the significance magnifies as the amounts increase. For example, a cream with a sg 0.95 would be 0.95gm in ever ml or cc – not much of an error, though it would float in water (which has a sg of 1). But, practically, an order for 1 gram of a cream could be successfully represented by 1 cc or 1 ml. A problem arises when the amounts increase and teh total variance becomes noticeable.

And “that’s the way it is”.