Man-made entities and objects are often designed with ease of use in mind. Mount Everest is difficult to ascend, but it was not made with climbing in mind; units of the metric system are easy to convert because they were designed with ease of conversion in mind. The metric system is a decimal system. This means that the units of the metric system differ by units of 10. Remember this, and you'll find converting metric-system units easy.

Move the decimal point three places to the right to convert from kilometers to meters; move the decimal point three places to the left to convert from meters to kilometers. For example: One kilometer equals 1,000 meters, and one meter equals 0.001 kilometers.

Move the decimal point two places to the right to convert from meters to centimeters; move the decimal point two places to the left to convert from centimeters to meters. For example: One meter equals 100 cm, and one centimeter equals 0.01 meters.

Move the decimal point one place to the right to convert from centimeters to millimeters; move the decimal point one place to the left to convert from millimeters to centimeters. For example: One centimeter equals 10 millimeters, and one millimeter equals 0.1 centimeters.

Move the decimal point three places to the right to convert from kilograms to grams; move the decimal point three places to the left to convert from grams to kilograms. For example: One kilogram equals 1,000 grams, and one gram equals 0.001 kilograms.

Move the decimal point two places to the right to convert from grams to centigrams; move the decimal point two places to the left to convert from centigrams to grams. For example: One gram equals 100 centigrams, and one centigram equals 0.01 grams.

Move the decimal point one place to the right to convert from centigrams to milligrams; move the decimal point one place to the left to convert from milligrams to centigrams. For example: One centigram equals 10 milligrams, and one milligram equals 0.1 centigrams.