GED Math: The Metric System

Okay. Yeah. The metric system. We’ve all heard of it, right? Like, you go to the store, an’ you buy a 2-liter of Coke. That’s metric, right? Liters. They don’t sell you a gallon or 2 quarts, but 2 liters. Meters, grams… we’ve all heard of that stuff. But in the U.S., you got quarts and gallons like I said instead of liters, and miles or yards or feet instead of meters, and ounces and pounds instead of grams. So, why two diff’rnt systems? Why it gotta be two different ways? An’ why you gotta know 2 kindsa measurement for your GED?

Truth is, most countries got the metric system cuz it’s easier. Yeah, that’s right… it’s easier. Hey, anything that makes things easier is okay by me, right? It can be hard to change over… that’s the problem. Think about all the highway signs that’d haveta change from miles to kilometers. Think of all the packaging that’d have to change from quarts to liters. Sounds like a big deal. But with all the other countries selling things in liters or grams, well, you can’t escape it. We got a global world, right? So the metric system comes creepin’ in, like with 2-liters. They sell ’em that way so they don’t have to make 2 kindsa bottles, one for the U.S. an’ one for everyone else. True dat. Since there’s metric measurements all over the place, you gotta know it for the GED.

So, what’d’ya need to know about the metric system? I’m tellin’ you, it’s easy. You jus’ gotta know a few things…

For measuring length (like how tall you are), you got meters. A meter is about how far a doorknob is from the floor.

For measuring weight (like how much you weigh), you got grams. A nickel weighs about 5 grams.

For measuring volume (like how much is in a soda bottle), you got liters. A 2-liter bottle is 2 liters. No kiddin’.

So those are, like, your basic measurements. You got a pretty good idea how much they are, right? Well, lots of stuff is bigger and smaller, so you gotta make bigger and smaller units to measure stuff with.

Here’s how it’s done. In the metric system, they add prefixes to the words…that’s another part of the word before the main word, like kilogram or centimeter. See how they got “meter” and “gram” in the word? The prefix, like kilo- or centi- tells you how many grams or meters you’re measurin’. An they go up an’ down by factors of 10. A factor means multiplying or dividing. So, a decimeter is a meter divided by 10 (1/10 of a meter), and a decameter is a meter multiplied by 10. Here are all the prefixes and what they mean:

Prefix Value Meters Liters Grams
kilo- x 1000 kilometers kiloliters kilograms
hecto- x 100 hectometers hectoliters hectograms
deca- x 10 decameters decaliters decagrams
(none) x 1 meters liters grams
deci- x .1 decimeters deciliters decigrams
centi- x .01 centimeters centiliters centigrams
milli- x .001 millimeters milliliters milligram

See how from milli- all the way up to kilo- they change by movin’ the decimal one place? That’s the beauty. You can change a number from milligrams to kilograms by jus’ movin’ the decimal. Watch this.

Say I got 403,495 grams. How many kilograms do I got? Well,  kilograms is 3 steps up from grams. So, I’m gonna move the decimal point (from the end, after the 5), 3 places to the left.

403,495 grams = 403.495 kilograms

That’s a lot easier than inches to miles, right? Cuz you just gotta move the decimal place. Got a metric system question you want me to answer? Or, any kinda measurement? Seriously, leave a comment, or e-mail

For more information about the GED test or GED test preparation, visit The GED Academy at or call 1-888-880-2164.

5 thoughts on “GED Math: The Metric System

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