Measurement Conversions: A Kid-Friendly Guide

If a water bottle holds 50 ounces, how many liters is that?

Or, if you are 5' 3" tall, how many centimeters is that?

In this guide, we'll show you how to convert these measurements in your head, in no time!

Read on for what metric and standard units are, instructions for converting between them, and a quick test to help you practice what you’ve learned.

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What Are the Units of Measurement?

Units of measurement are tools that help us express proportions such as length, mass, volume, and more in a way that everyone understands—through numbers. 

You go for a run, and a friend asks, "How far did you go?" 

You could say, "Pretty far," but that’s vague – “pretty far” may not mean the same thing to your friend as it does to you. 

But when you say "I ran 2.5 miles," it gives a precise answer.

That’s the purpose of measurement units: to give clear answers everyone can understand.

This is where things get tangled: There are many types of measurement units and ways to measure.

Long ago, each civilization had its own ways of measuring. Ancient Egyptians used cubits (based on a forearm’s length), and Romans measured distances in paces. Some cultures even used grains of barley to measure mass!

The problem? 

These units weren’t always the same—a cubit in one region might be longer than in another. Imagine trying to follow a recipe where no one agrees on how much a "cup" is!

To avoid confusion, the world now relies on two main systems of measurement:

• The Standard System 

• The Metric System 

Let’s explore each of them!

Units of the Standard System

The standard system is used in countries like the United States, Myanmar, and Liberia. 

The standard system came from crafty ways of measuring things using everyday objects such as body parts, familiar tools, or natural distances to measure. 

For example:

• A foot was about the length of an actual foot.

• An inch was originally the width of a thumb.

• A yard was roughly the length of a belt or sash.

• A mile was based on 1,000 paces in ancient Rome.

To use the standard system, we need to know specific conversion values for each unit.

Length

• 1 foot = 12 inches

• 1 yard = 3 feet = 36 inches

• 1 mile = 1,760 yards = 5,280 feet 

Mass

• 1 pound = 16 ounces

• 1 ton = 2,000 pounds = 32,000 ounces

Volume

• 1 cup = 8 fluid ounces

• 1 pint = 2 cups = 16 fluid ounces

• 1 quart = 2 pints = 4 cups

• 1 gallon = 4 quarts = 8 pints = 16 cups

The standard system doesn’t follow a clear mathematical pattern, so we have to memorize values before we jump into conversions.

Units of Metric System

The metric system is a system of measurement used by most countries, including Canada, France, and China. 

Because it is mathematically intuitive, we use this system in math, science, medicine, and international trade.

It’s based on the powers of ten. In other words, each step up or down in unit size is always 10 times bigger or smaller than the next. This makes conversions between units quite simple.

At the start, there’s always a base unit like:

• Meter (m) for length

• Liter (L) for volume

• Gram (g) for mass

To create larger or smaller units, we multiply or divide by 10:

• Moving to a larger unit? Divide by 10, 100, or 1,000.

• Moving to a smaller unit? Multiply by 10, 100, or 1,000.

To make things even more understandable, the metric system often uses Latin and Greek prefixes to show us exactly how much bigger or smaller a unit is compared to the base. 

• Larger units have prefixes that mean "more" (kilo-, hecto-, deca-)

• Smaller units have prefixes that mean "less" (deci-, centi-, milli-)

For example, a kilometer (km) is larger than a meter (m), while a millimeter (mm) is smaller than a meter.

Think of it as a staircase with the base unit in the middle. Each step up divides by 10, and each step down multiplies by 10—prefixes show the change! 

A Trick to Remember the Metric Unit Scale

As we advance on our math journey, the metric unit prefixes start to feel like second nature. 

For example, we know that a decimeter is 10 times larger than a centimeter, and a kilometer is 1,000 times larger than a meter.

However, there’s also a shortcut.

Just like other math concepts, mnemonics can help! One popular trick is:

King Henry Died By Drinking Chocolate Milk.

Each word represents a metric unit:

• King → Kilo-

• Henry → Hecto-

• Died → Deca-

• By → Base unit (meter, liter, gram)

• Drinking → Deci-

• Chocolate → Centi-

• Milk → Milli-

So next time you need to convert, just think of King Henry!

Check out our video tutorial on the metric system.

Measurement Conversions: Standard to Standard

When converting between standard units, we follow these simple rules:

• When converting to a smaller unit, multiply because more of the smaller unit fits into the larger one.

• When converting to a larger unit, divide because fewer of the larger units fit into the smaller one.

Let’s see this in action!

Examples of Length Conversions

We’ll convert 5 feet to inches.

• We know that 1 foot = 12 inches

• So, 5 × 12 = 60 inches

Next, we’ll convert 36 inches to yards.

• We know that 1 yard = 36 inches

• 36 ÷ 36 = 1 yard

Examples of Weight Conversions

First, we’ll convert 4 pounds to ounces.

• We know that 1 pound = 16 ounces

• 4 × 16 = 64 ounces

Next, we’ll convert 32 ounces to pounds.

• We know that 1 pound = 16 ounces

• 32 ÷ 16 = 2 pounds

Examples of Volume Conversions

First off, we’ll convert 3 gallons to quarts.

• We know that 1 gallon = 4 quarts

• 3 × 4 = 12 quarts

After that, we’ll convert 8 cups to pints.

• We know that 1 pint = 2 cups

• 8 ÷ 2 = 4 pints

Measurement Conversions: Metric to Metric

We already have a good idea of how metric units work, but now let’s focus on how to convert between them.

Since all metric units are based on powers of 10, we can convert between them in a simple way:

• Moving to a larger unit: Move the decimal to the left (same as dividing by 10, 100, or 1,000, depending on the steps).

• Moving to a smaller unit: Move the decimal to the right (same as multiplying by 10, 100, or 1,000).

Let’s convert 25.4 centimeters (cm) to millimeters (mm).

Since we’re moving one step down to a smaller unit, we shift the decimal point one place to the right:

25.4 → 254 mm (which is the same as 25.4 x 10 = 254)

But what if the units are farther apart on the metric scale?

For example, how would you convert 75 centiliters (cL) to hectoliters (hL)?

Of course, if we know the metric scale by heart, we can do the math right away!

Since centiliters (cL) and hectoliters (hL) are four steps apart on the metric scale (moving up or left), we move the decimal point four places to the left like so:

75.0 → 7.50 → 0.750 → 0.0750 → 0.0075 hL

So, 75 cL = 0.0075 hL.

If we don’t know the scale by heart, we can use the King Henry Died By Drinking Chocolate Milk mnemonic to count the steps:

1. King → Kilo-liter

2. Henry → Hecto-liter (We’re converting to here ↓)

3. Died → deca-liter

4. By → Base Unit - liter

5. Drinking → Deci-liter

6. Chocolate → Centi-liter (We’re converting from here ↑)

7. Milk → Milli-liter

From C to H, we’re moving 4 steps (up or to the left). That means we move the decimal four places to the left:

75.0 → 7.50 → 0.750 → 0.0750 → 0.0075 hL

And that’s how we can convert between all metric units of the same type—whether it’s length, volume, or mass.

Measurement Conversions: Standard to Metric

When converting between standard and metric units, we have to know the key conversion values.

Unlike the metric system, where we can simply move the decimal, converting between these two systems requires memorization and a bit of math.

That’s why we’ve put together this handy reference chart with the most common conversions for length, mass, and volume!

Standard Unit	Metric Equivalent
Length
1 inch (in)	2.54 centimeters (cm)
1 foot (ft)	30.48 centimeters (cm)
1 yard (yd)	0.9144 meters (m)
1 mile (mi)	1.609 kilometers (km)
Mass
1 ounce (oz)	28.35 grams (g)
1 pound (lb)	0.4536 kilograms (kg)
1 ton (US)	907.18 kilograms (kg)

Standard Unit	Metric Equivalent
Volume
1 fluid ounce (fl oz)	29.57 milliliters (mL)
1 cup	236.59 milliliters (mL)
1 pint (pt)	473.18 milliliters (mL)
1 quart (qt)	0.946 liters (L)
1 gallon (gal)	3.785 liters (L)

Since there’s no special math rule that connects the two systems, you won’t have to do these conversions very often in your math work. And when you do, this chart will have your back! 

With eyes on the chart, let's convert the following measurements!

First, we’ll convert 5 feet to centimeters.

• 1 foot = 30.48 cm

• 5 × 30.48 = 152.4 cm

Next, we’ll convert 3 pounds to kilograms

• 1 pound = 0.4536 kg

• 3 × 0.4536 = 1.3608 kg

Finally, we’ll convert 2 quarts to liters

• 1 quart = 0.946 L

• 2 × 0.946 = 1.892 L

Try It Yourself: Convert These Measurements

Now it’s your turn! Use what you’ve learned to convert these measurements and scroll down to check your answers. 

1. Convert 6 feet to inches.

2. Convert 5 gallons to quarts

3. Convert 250 milliliters to liters

4. Convert 10 miles to kilometers

5. Convert 3 kilograms to pounds

Master Measurement Conversions at Mathnasium of Littleton

Mathnasium of Littleton is a math-only learning center for K-12 students in Littleton, CO.

Using a proprietary teaching approach—the Mathnasium Method™, our specially trained math tutors provide face-to-face instruction in an engaging environment to help students master any math topic, including measurement conversions, typically covered in elementary and middle school math. 

Students start their Mathnasium journey with a diagnostic assessment that allows us to understand their specific strengths and knowledge gaps. Guided by assessment-based insights, we create personalized learning plans that will put them on the best path toward math mastery. 

Whether your student is looking to catch up, keep up, or get ahead in their math class, schedule an assessment, and enroll at Mathnasium of Littleton today! 

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Pssst! Check Your Answers Here

If you’ve given our exercises a try, check your answers below:

1) Convert 6 feet to inches.

• 1 foot = 12 inches

• 6 × 12 = 72 inches

2) Convert 5 gallons to quarts.

• 1 gallon = 4 quarts

• 5 × 4 = 20 quarts

3) Convert 250 milliliters to liters.

• 1,000 mL = 1 L

• 250 ÷ 1,000 = 0.25 L

4) Convert 10 miles to kilometers.

• 1 mile = 1.609 km

• 10 × 1.609 = 16.09 km

5) Convert 3 kilograms to pounds.

• 1 kilogram = 2.2046 pounds

• 3 × 2.2046 = 6.614 pounds

How did you do?