Converting Between U.S. and Metric Systems of Measurement
Converting Between U.S. and Metric Systems of Measurement
Many measurements in the United States are made in metric units. A drink may come in \(\text{2-liter}\) bottles, calcium may come in \(\text{500-mg}\) capsules, and we may run a \(\text{5-K}\) race. To work easily in both systems, we need to be able to convert between the two systems.
The table below shows some of the most common conversions.
| Conversion Factors Between U.S. and Metric Systems | ||
|---|---|---|
| Length | Weight | Volume |
| \(1\) in = \(2.54\) cm
|
\(1\) lb = \(0.45\) kg
|
\(1\) qt = \(0.95\) L
|
We make conversions between the systems just as we do within the systems—by multiplying by unit conversion factors.
Example
Lee’s water bottle holds \(500\) mL of water. How many fluid ounces are in the bottle? Round to the nearest tenth of an ounce.
Solution
| 500 mL | |
| Multiply by a unit conversion factor relating mL and ounces. | \(500\phantom{\rule{0.2em}{0ex}}\text{mL}·\frac{1\phantom{\rule{0.2em}{0ex}}\text{fl oz}}{30\phantom{\rule{0.2em}{0ex}}\text{mL}}\) |
| Simplify. | \(\frac{500\phantom{\rule{0.2em}{0ex}}\text{fl oz}}{30}\) |
| Divide. | \(16.7\phantom{\rule{0.2em}{0ex}}\text{fl. oz.}\) |
| The water bottle holds 16.7 fluid ounces. |
The conversion factors in the table above are not exact, but the approximations they give are close enough for everyday purposes. In the example above, we rounded the number of fluid ounces to the nearest tenth.
Example
Soleil lives in Minnesota but often travels in Canada for work. While driving on a Canadian highway, she passes a sign that says the next rest stop is in \(100\) kilometers. How many miles until the next rest stop? Round your answer to the nearest mile.
Solution
| 100 kilometers | |
| Multiply by a unit conversion factor relating kilometers and miles. | \(100\phantom{\rule{0.2em}{0ex}}\text{kilometers}·\frac{1\phantom{\rule{0.2em}{0ex}}\text{mile}}{1.61\phantom{\rule{0.2em}{0ex}}\text{kilometers}}\)
|
| Simplify. | \(\frac{100\phantom{\rule{0.2em}{0ex}}\text{mi}}{1.61}\) |
| Divide. | 62 mi |
| It is about 62 miles to the next rest stop. |
Optional Video: American and Metric Conversions
This lesson is part of:
Properties of Real Numbers