Just like our number system in general, the metric system is based on tens.

The names of metric unit use a base word and a prefix that stands for a power of ten.

For example, the standard unit of length is the meter. Prefixes are added to the word "meter" to form words that describe thousandths of a meter, hundredths of a meter, and 1,000 meters. (Other prefixes are used as well, but are far less common.

It is helpful to think of real-world objects that relate to each of the measurements.

1 kilometer is about the distance a person can walk in ten minutes

1 meter is about the height of a kitchen counter

1 centimeter is about the width of a child's finger

1 millimeter is about the width of the tip of a pen

Conversions

When asked to convert between metric measurements, it is often good to think of a similar, yet easier problem, and then relate that problem to the one that is given.

For example: 250 centimeters = ? meters

Since 100 centimeters = 1 meter, then 200 centimeters = 2 meters. Also, since 100 centimeters = 1 meter, then 50 centimeters would be half of a meter or 0.5 meter.

So.... 250 centimeters = 2.5 meters

The problem can also be thought of as dividing 250 by 100, since there are 100 centimeters in 1 meter. A shortcut for dividing by 100 is moving the decimal point 2 spots to the left.

Another example: 3.3 meters = ? millimeters

One way of looking at this problem is to think of a millimeter being one-thousandth of a meter.

Rewrite 3.3 as 3.300 and think about how many thousandths that is all together. It is 3,300 thousandths. Since millimeters are thousandths...

3.3 meters is 3,300 millimeters

Mass

The standard unit of mass in the metric system is the gram.

The prefixes