To read a metric scale, it is necessary to understand the metric system of measurement. Whereas the American system is based on units of inches and feet, the metric system is based on units called millimeters, centimeters and meters.
There are 10 millimeters in a centimeter, and 100 centimeters in a meter. For reference, keep in mind that 1 meter equals approximately 3 feet, 3 inches.
A metric scale on a ruler uses one- and two-letter abbreviations for units of measure. A millimeter is abbreviated as ?mm,? a centimeter as ?cm? and a meter as ?m.? Look for this abbreviation toward the end or on the corner of the metric ruler. If the abbreviation is ?mm,? that means the digits printed on the ruler refer to millimeters. Generally the numbers are marked in units of 10, with smaller marks between the major dividers signifying individual millimeters. This type of ruler is used for measuring very small objects and distances.
If the abbreviation on the corner of the ruler reads ?cm,? that means the ruler is numbered in centimeters. Each major divider represents one centimeter, with the smaller marks between representing millimeters.
Express these measurements in decimals. For example, a paper clip measured against the cm ruler reaches to 4 marks past the 3 cm mark. This means the paperclip is 3 cm and 4 mm long, which can also be expressed as 3.4 cm. Other metric measurement scales include grams and kilograms instead of pounds and ounces.