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3.22: Conversion Estimation between Systems of Measure

Difficulty Level: At Grade Created by: CK-12
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Have you ever measured liquid?

Let's say that you wanted to make a cake which needed 2 cups of milk. Could you estimate a conversion of two cups of milk to liters?

This Concept will teach you how to estimate between customary and metric units of measurement.


While you encounter the Customary System of measurement all of the time in your everyday life, there is another system of measurement that is also widely used. This system is known as the Metric System. In other countries people use the metric system for the same things that we use the customary system for. We might weigh grapes using pounds, but in France they use grams to weigh grapes. You may measure the length of one side of your backyard in feet, but in Beijing they use meters. Even in the United States, the metric system is frequently used especially in science.

You may find yourself in a situation where you need to convert between the metric system and the customary system. Take a look at the chart below. It shows the estimated customary equivalent to common metric units.

Metric Units Customary Units
1 centimeter 0.39 inches
1 meter 3.28 feet
1 kilometer 0.62 miles
1 milliliter 0.2 teaspoons
1 liter 4.23 cups
1 gram 0.04 ounces
1 kilogram 2.2 pounds

Using this chart can help us to estimate the equivalence between metric units of measurement and customary units of measurement. Let’s look at a problem.

Estimate the equivalent measures from 14 centimeters to inches.

A centimeter is equal to about 0.39 inches, so we multiply \begin{align*}14 \cdot 0.39 = 5.46 \ inches\end{align*}

Estimate the equivalent measures from 7.7 pounds to kilograms.

There are 2.2 pounds in 1 kilogram, so we divide the number of pounds by the number of pounds in 1 kilogram. \begin{align*}7.7 \div 2.2 = 3.5\end{align*}

The answer is 3.5 kilograms.

If you keep this chart in mind, you will always be able to estimate measures. If you do this enough, you will be able to figure some of them out without the chart.

Most runners know that a 5k race is about 3.1 miles. Where as a 10k is 6.2 miles.

Here are a few for you to try on your own. Estimate each equivalent metric measure.

Example A

.16 ounces = ____ grams

Solution: 4 grams

Example B

6 pounds = ____ kilograms

Solution: 3 kilograms

Example C

12 feet = ____ meters

Solution: 3 meters

Here is the original problem once again.

Let's say that you wanted to make a cake which needed 2 cups of milk. Could you estimate a conversion of two cups of milk to liters?

To convert cups to liters, let's think about how many cups equals 1 liter.

4.23 cups is equal to 1 liter.

Our recipe calls for a little less than half the cups needed to equal 1 liter.

Therefore, we can say that 2 cups is approximately equal to .5 liters.

This is our answer.


Here are the vocabulary words found in this Concept.

Customary System
a system of measurement common in the United States. It involves units of measurement such as inches, feet, miles.
Metric System
a system of measurement developed by the French and common in Europe. It involves meters, grams, liters.

Guided Practice

Here is one for you to try on your own.

How many cups is 16 liters?


To figure this out, we can use the equivalent measure of cups to liters.

4.23 cups = 1 liter

We can round down to 4 cups = 1 liters to estimate accurately.

Now we want to figure out the number of cups in 16 liters, so we can multiply to figure this out.

\begin{align*}4 \times 16 = 64\end{align*}

There are about 64 cups in 16 liters.

Video Review

Here is a video for review.

- This is a Khan Academy video on customary and metric units of measurement.


Directions: Estimate a customary equivalent for the following metric measurements.

1. 4 kilograms to pounds

2. 7.5 meters to feet

3. 6 liters to cups

4. 13.25 kilometers to miles

5. 6 kilometers to miles

6. 8 liters to cups

7. 20 kilograms to pounds

8. 12 meters to feet

Directions: Estimate a metric equivalent for the following customary measurements, round to the nearest hundredth where necessary.

9. 4 quarts to liters

10. 34 ounces to grams

11. 52 pounds to kilograms

12. 9 inches to centimeters

13. 14 feet to meters

14. 16 cups to liters

15. 5 miles to kilometers

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Customary System

The customary system is the measurement system commonly used in the United States, including: feet, inches, pounds, cups, gallons, etc.

Metric System

The metric system is a system of measurement commonly used outside of the United States. It contains units such as meters, liters, and grams, all in multiples of ten.

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Difficulty Level:
At Grade
Date Created:
Nov 30, 2012
Last Modified:
Jul 06, 2016
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