Metric Systems and English Systems of Measurement (2024)

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In the metric system, each basic type of measurement (length, weight, capacity) has one basic unit of measure (meter, gram, liter). Conversions are quickly made by multiplying or dividing by factors of 10. It is as simple as moving the decimal point to the right (for smaller prefixes) or to the left (for larger prefixes).

To remember the proper movement, arrange the prefixes from largest to smallest.

Conversion Ratio (or Unit Factor): A conversion ratio (or unit factor) is a ratio equal to one. This ratio carries the names of the units to be used in the conversion. It can be used for conversions within the English and Metric Systems, as well as for conversions between systems. The conversion ratio is based upon the concept of equivalent values. In the example below, 1000 meters is substituted for its equivalent measure of 1 kilometer.

Convert 10.25 kilometers to meters.
Notice in the listing above that meter is three places to the right of the prefix kilo. This tells us to move the decimal point three places to the right. The answer is 10,250 meters.

(Problem using dimensional analysis) Convert 4.5 kilometers to millimeters. 1 km = 1,000,000 mm

Convert 650 mL to daL. [mL is milliliters and daL is decaliters].
Notice in the listing above that the prefix deca is four places to the left of the prefix milli. This tells us to move the decimal point four places to the left. The answer is 0.0650 daL. (Note: dL is deciliters, daL is decaliters.)

Convert 750 grams to milligrams.
Notice in the listing above that the prefix milli is three places to the right of gram. This tells us to move the decimal point three places to the right. The answer is 750,000 milligrams.

While the metric system was lawfully accepted for use in the United States in 1866, the US has not adopted the metric system as its "official" system of measurement.

The US English System of measurement grew out of the manner in which people secured measurements using body parts and familiar objects. For example, shorter ground distances were measured with the human foot and longer distances were measured by paces, with one mile being 1,000 paces. Capacities were measured with household items such as cups, pails (formerly called gallons) and baskets.

Obviously this system allowed for discrepancies between measurements obtained by different individuals. A standard was eventually set to ensure that all measurements represented the same amount for everyone.

NOTE: As with all mathematical problems, there are other ways to arrive at these answers. Most other methods utilize the concept of the conversion ratio, but may be written in a different manner or calculated mentally.