Metric Math Units: Help for Fifth Grade Students

Using Metric Units in Math

First, let's review the metric units of measurement. For mass, the gram (g) is the basic unit of measure, and 1,000 grams equal one kilogram (kg). Length is measured in meters (m), and one kilometer (km) equals 1,000 meters. Smaller lengths are measured using centimeters (cm), which are equal to 1/100 of a meter. Liquid volume can be measured in liters (l) or in milliliters (ml), which are 1/1,000 of a liter.

Converting Metric Units

You'll often be asked to convert one type of metric unit to another. For instance, you might need to convert kilograms to grams or meters to kilometers. No matter what units you're converting, you can follow these rules:

1. If you're converting a smaller-sized unit to a larger unit, like grams to kilograms, you'll divide the number of smaller units by the number of those units that make up the larger unit. For instance, if you're converting 5,000 grams to kilograms, you'd divide 5,000 by 1,000 to get five kilograms (5,000 ÷ 1,000 = 5), since 1 kg = 1,000 g.
2. If you're converting a larger-sized unit to a smaller unit, like kilometers to meters, you have to multiply the number of larger units by the amount of smaller units that it takes to make up the larger unit. For example, to convert three kilometers to meters, you would multiply three by 1,000 to get 3,000 meters (3 x 1,000 = 3,000), because 1 km = 1,000 m.
3. Always make sure your answer is reasonable. If you're converting a larger unit into a smaller unit, then your answer should be larger than the one you started with; if you're converting a smaller unit to a larger unit, your answer should be smaller than the initial number.

Cubic Volume

In fifth grade, you'll learn to measure the volume of solid, 3-dimensional objects using cubic units. A cubic unit is simply a cube that has a certain unit of measurement as its length, width and height. For instance, a cubic centimeter is 1-centimeter long, wide and tall. Similarly, a cubic meter has a length, width and height of one meter.

A solid object's volume is determined by the number of cubic units that it's made up of. For instance, a rectangular block that is made up of 40 individual 1 cm x 1 cm x 1 cm blocks would have a volume of 40 cubic centimeters.