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5 Tips for Understanding Weights and Measures

How much is a fluid ounce? How about a milliliter? Or a gallon? If you don't have an intuitive feel for exactly how much volume these quantities represent, keep on reading!

By
Jason Marshall, PhD
Episode #209

Tip 4: Pints, Quarts, and Gallons (Oh My!)

Since 1 fluid ounce is a pretty tiny amount of liquid (as evidenced by the dinky medicine cup,) it's no wonder that we commonly use larger units to measure volumes of everyday things like beverages and gasoline. For example, 8 fluid ounces of a liquid is known as 1 cup—a fact which those of us who use measuring cups to cook with are no doubt intimitely acquainted with.

Creating new units of volume is fun, so people didn't stop there.

Creating new units of volume is fun, so people didn't stop there. Two cups is also known as 1 pint which--fun fact--is roughly the volume of air that humans inhale and exhale during a typical breath. It's also the most common size of a paper carton of cream or half-and-half.

Marching up this liquid ladder, two pints (which is also 4 cups) is known as 1 quart, and 4 quarts is known as 1 gallon. Notice that the word "quart" is part of the word "quarter"—can you guess why? It's because it's a quarter gallon! A quart is the size of those tall, skinny, paper milk cartons, a half gallon is the size of the wider paper milk cartons, and 1 gallon is the size of a large plastic jug of milk. Thirsty?

Of course, the fluid ounce isn't the only way we measure volume. In fact, most of the world uses an entirely different system to do so! It's called the metric system, and it's what all the cool kids are using these days. In this system, we measure volume using liters and millileters. One liter is made up of 1,000 millileters, so it's very easy to do calculations and convert back and forth between either.

What does a millileter look like? If you're familiar with teaspoon and tablespoon measurements, then it's helpful to know that 1 teaspoon is about 5 millileters (abbreviated 5 mL.) So 1 millileter is a bit less than a quarter teaspoon. Like a fluid ounce, a millileter isn't very much volume.

And that's exactly why we don't often use millileters when buying bottles of refreshing beverage items from the grocery store, or fuel for our cars. Instead, we use the millileter's big sibling, the liter. Soft drinks are often sold in 1- and 2-liter bottles, and in Europe and much of the rest of the world, gasoline is priced and sold by the liter.

Just in case you're wondering, there are 3.785 liters in 1 gallon.

Wrap Up

OK, that's all the weights and measures we have time for today—but rest assured, it's a topic we'll be returning to soon!

Please be sure to check out my book, The Math Dude’s Quick and Dirty Guide to Algebra. And remember to become a fan of The Math Dude on Facebook, where you’ll find lots of great math posted throughout the week. If you’re on Twitter, please follow me there, too.

Until next time, this is Jason Marshall with The Math Dude’s Quick and Dirty Tips to Make Math Easier. Thanks for reading, math fans!

Weights image courtesy of Shutterstock.