# Centigram

A centigram (cg) is a unit of weight/mass in the International System of Units (SI), the modern form of the metric system of measurement.

100,000 centigrams = 1 kilogram

100 centigrams = 1 gram

Below are some relationships between centigrams and units of mass in the US customary system of measurement:

1 centigram = 0.000353 (3.53e-4) ounces

1 centigram = 0.000022 (2.2e-5) pounds

As can be seen, the centigram is a very small unit of measurement relative to units of mass that are used to measure many everyday objects. For example, a person who weighs 60 kilograms weighs 6,000,000 centigrams, so discussing mass in terms of kilograms is more convenient. This is one of the benefits of SI; values can easily be expressed using units that denote various multiples of 10, so a person can easily adjust the units used to present data that reflects the desired magnitude. This is part of the reason that centigrams are not widely used for everyday measurements; they are more likely to be used in laboratory settings for precise measurements of mass.

Another reason centigrams may not be commonly used is because grams and milligrams are two other units of mass that are used relatively frequently, both of which are similar in magnitude to centigrams. Most things that may be expressed in centigrams can likely be effectively expressed in either grams or milligrams, two more well-known and used units of measurement.

## SI prefixes

The International System of Units (SI) makes use of SI prefixes (milli-, centi-, kilo-, etc.) to denote multiples or submultiples of a base unit that are related by a power of 10. The base unit of mass in SI is the kilogram. The kilogram is unique as a base unit in that it is the only base unit that already has an SI prefix, kilo-, indicating that 1 kilogram is 10^{3} grams. All other base units in SI such as meters, seconds, moles, etc., do not have prefixes.

Since SI does not allow for the use of multiple prefixes (e.g. "kilomilligram") to modify a base unit, prefixes are added to the gram, rather than kilogram, to denote different multiples or submultiples of mass.

1 centigram = 10^{-5} kilograms

1 centigram = 10^{-2} grams

1 centigram = 10^{-1} decigrams

1 centigram = 10^{1} milligrams

Remembering SI prefixes and what power of 10 they represent is helpful because it allows us to choose the most appropriate unit for whatever is being measured. For example, a housefly weighs approximately 1 centigram. If its mass were measured in kilograms instead of centigrams, the housefly would weigh 0.00001 kilograms, which is more difficult to work with than 1 centigram, particularly when performing any calculations.

It is also important to be able to convert between various measurements of mass in different systems, particularly from US customary units to SI, since SI is the standard used throughout most of the world.

Examples

Convert the following measurements to centigrams and kilograms.

1. 12 pounds:

There are 0.000022 pounds in 1 centigram, or 45,359.24 centigrams in 1 pound, so:

12 × 45,359.24 = 544,310.88 cg

544,310.88 × 10^{-5} = 5.443 kg

2. 2 ounces:

There are 0.000353 ounces in 1 centigram, or 2,834.952 centigrams in 1 ounce, so:

2 × 2,834.952 = 5,669.904 cg

5,669.904 × 10^{-5} = 0.057 kg