In today’s global market, it is important to know how to use the metric system because every country except America uses it! Because it is a base 10 system, it is easy to convert the basic units without doing any calculations!

The metric system starts with a base unit, and then adds prefixes to measure larger or smaller units. The prefixes of each metric unit tell you how many times the base unit it is. For example, the base unit for length in the metric system is the meter. If we add the prefix “kilo” to it, it means “1000 times the base unit.” So one kilometer is equal to 1000 meters. At the other end of the spectrum, we could add “milli,” meaning “one one-thousandth of the base unit.” So one meter is equal to 1000 millimeters. There is a prefix for every 10-times the base unit.

All the prefixes can be lined up on either side of the base unit, and for the basic prefixes, each one is either 10 more times the base unit (on the large side), or an additional tenth of the base unit (on the small side). When all written out, it looks like this:

Kilo (1000X base), Hecto (100X base), Deka (10X base), BASE UNIT, Deci (1/10X base), Centi (1/100X base), Milli (1/1000X base)

There are more prefixes that are further away, but these are the basic prefixes.

Because these are all in base 10, we don’t actually have to do any math to convert from any of these units to another. All we have to do is move the decimal place the same number of times in the same direction it takes to get from one prefix to another.

For example, if we wanted to convert 1 (1.0) centimeter to meters, we would move the decimal two places to the left, to get 0.01 meters. To go from 2.3 kilometers to centimeters, we would move the decimal 5 places to the right, to get 230,000 centimeters. Always use zeros to fill in the rest of the decimal places.

Create a mnemonic device to help you remember the order of the prefixes. I always use:

Kids Hate Doing Metrics Dirty Crummy Metrics

Kids (kilo) Hate (Hecto) Doing (Deka) Metrics (Meter) Dirty (Deci) Crummy (Centi) Metrics (Milli)

This is for length, where M is for meter, but you can just replace meter with any other base unit, such as grams or liters. Just be careful not to mix up Deka and Deci, as they both start with D. Don’t mix up meter and milli either.

For teachers, it’s fun to have the students come up with their own mnemonic devices for these. Others I’ve seen are:

Kings Have Diamonds But Diamonds Cost Money

Kings (Kilo) Have (Hecto) Diamonds (Deka) But (Base unit) Diamonds (Deci) Cost (Centi) Money (Milli)

Kittens Hate Dogs But Dogs Care More

Kittens (kilo) Hate (Hecto) Dogs (Deka) But (Base unit) Dogs (Deci) Care (Centi) More (Milli)