The base units in the metric system – International System of Units (S.I.) – are as follows:

- Meter – to measure distance
- Liter – to measure capacity (solids or liquids)
- Gram – to measure weight

**The correct order of metric units in order from smallest to largest is as follows. **

**milli-*: 1/1000 of a unit**

**centi-*: 1/100 of a unit**

**deci-: 1/10 of a unit**

**the unit itself*- (1)**

**deka-: 10 units**

**heckto-: 100 units**

**kilo-:* 1,000 units***

*Most commonly used measurements. For example, rather than saying “one hectometer,” the common usage is “100 meters.”

Rather than saying “one decimeter,” the usage is “10 centimeters.”

Combine the above numerical prefixes with the above-mentioned base units to indicate units of 10 or tenths of a unit, depending on the unit’s position in the metric hierarchy.

Also, note how measures of each unit are expressed on base 10 amounts. As the measurements proceed from smaller to the next higher, the number of zeros decreases.

Here’s an example using distance:

A millimeter is .001 of a meter.

A centimeter is .01 of a meter.

A kilometer is 100,000 centimeters.

Watch this amusing and informative YouTube video on using the metric system as units of measurement.

Table of Contents

## Converting metric to U.S. measurements

### Meters – Units of Length

1 kilometer = 0.62 mile

1 meter = 3.28 feet

### Liters – Solid or Liquids Capacities

1 liter = 1.06 quarts

### Grams – Units of Weight

1 gram = 0.035 ounces

1 kilogram = 2.204 pounds

1 metric ton = 2204.62 pounds

## Converting U.S. standard units to metric

### Length

1 inch = 2.54 centimeters

1 foot = 30.48 centimeters

1 yard = 0.914 meters

1 mile = 1.609 kilometers

### Capacity

1 liquid ounce = .029 liters

1 pint = 0.473

1 quart = 0.946 liters

1 gallon = 3.785 liters

### Weight

1 ounce = 28.34 grams

1 pound = 0.454 kilograms

1 ton = 907.185 kilograms

## Measuring Temperature

Most countries using the metric system use the Celsius or centigrade measurement scale. This scale is based on zero degrees as the freezing point of water and 100 degrees as the boiling point.

The Celsius measurement is named after the 18th-century Swedish astronomer Anders Celsius.

The counterpart for Celsius is the Fahrenheit scale, named after an 18th-century physicist, Daniel Gabriel Fahrenheit.

Fahrenheit was the scale first used in the new mercury-in-glass thermometer. Nowadays, the United States is the only industrialized country to exclusively use Fahrenheit temperature measurements.

### Converting Celsius to Fahrenheit (and vice versa)

Use the following conversion formulae:

**Celsius to Fahrenheit (°C to °F):**

(°C x 9/5) + 32 = °F

Thus, to convert 20°C to °F: (20°C x 9/5) + 32 = 68°F

**A shortcut** for an approximate value is to multiply the °C x 2 and add 30.

Thus, 20° C x 2 + 30 = ~70° F (two degrees away from the precise answer, but close enough for a quick guess)

*Fahrenheit to Celsius (°F to °C)*

*Fahrenheit to Celsius (°F to °C)*

(°F – 32) x 5/9 = °C

Thus, to convert 68°F to °C: (68 – 32) x 5/9 = 20°C

A shortcut for an approximate value is to subtract 30 from the °F and divide by 2.

Thus, 68°F-30 = 38. Divide the result by 2 = ~19° (one degree below the precise answer, and, again, close enough for quick guesswork.)

Watch this YouTube video for more examples.

## A brief history of the metric system

The father of the metric system is generally recognized as Gabriel Mouton, a 17th-century French clergyman.

Mouton originally proposed a system of measurement based on the decimal. French scientists spent years refining the system until its first practical application was during the French Revolution in 1799.

The French revolutionary government replaced their existing non-standard trade systems and used a decimal-based system based on the kilogram and the meter (or French metre).

The basic units were extracted from the dimensions of the Earth for length, and the volume of water in a cubic decimeter to measure volume.

By 1850, James Clerk Maxwell, a Sottish scientist and mathematician, devised the present metric system.

Maxwell’s system introduced a small number of base units (meters, liters, grams), which is the basis for the modern metric system, along with other scientific refinements to achieve standardization.

## What are some advantages of the metric system?

### The system is standard throughout the world

Non-metric measurements can be (and have often been) varied between countries. In the olden days, a yard could be measured from the tip of a ruler’s nose to the end of his or her finger.

With the metric system, we can be confident that meters, liters, and kilograms are the same, whether in the UK, Canada, France, Germany, and other countries worldwide.

That standardization has apparent advantages for international trade and avoiding errors and misunderstandings in machinery, manufacturing, and joint space exploration ventures.

### The metric system is decimal-based

As illustrated above, a base-ten system is easy to convert between units, no matter what is being measured.

To move between measurements, you either multiply or divide by 10, 100, 1000, and so forth.

From higher to lower, you just move the decimal point to the appropriate number of spaces, e.g., 1.0 kilometers = 1,000 meters.

### The metric system is easy to use

Calculating metric measurements is easier and simpler than, say, adding pounds and ounces, feet and inches, multiplying miles by 5,280 to arrive at the number of feet, or multiplying by 1,760 to calculate the number of yards.

### The metric system employs a standard naming convention

The metric system, as demonstrated above, employs standard prefixes for its base units. This quickly demonstrates how one unit compares to the next higher or lower measurement.

Contrast that to feet versus inches (12:1) or ounces versus pounds (16:1).

### The metric system is future-proof

Judging by past adoptions – e.g., the UK in 1965 – the metric system is destined to emerge as the only accepted measurement system in the world.

Countries remaining on an exclusively non-metric system risk being left behind in global trade.

## The U.S. is still not fully on board the metric train

The United States has had a relationship with the metric system dating back to its colonial days.

Even though the metric system is not part of American daily life, the U.S. government has agreed to use the metric system in international trade.

Nevertheless, weights and measures remain chaotic in the U.S. Consider the following:

- American football fields are measured in yards.
- Track meets and races are run in meters.
- Mechanics use horsepower (foot-pounds per second) to see how powerful automobile engines are – but measure the engine’s displacement in terms of liters.
- PSI and Millibars for air pressure aloft are used for measuring air pressure.

All of the above are examples of the so-called U.S. Customary System. That inch-pound system has more than 300 different units that measure all types of physical quantities.

We also express different weights in tons to weigh coal, for example.

### The apathetic history of metric conversion in the U.S.

So, why doesn’t the U.S. throw all that out and convert completely to the metric system? The short answer is that American colonists were British subjects and used the British system.

Neither the Americans nor the British found any reason to imitate the French.

The British system evolved from a non-standard system of weights and measures dating back to medieval times.

As France developed the more scientific metric system during the turbulent years of the French Revolution, England and its American colonies stayed with the British system.

As the colonies gained independence and eventually a new Constitution, Congress had the power to “fix the Standard of Weights and Measures.”

As George Washington’s Secretary of State, Thomas Jefferson recommended a decimal system for measurement but didn’t want to deal with the French by paying for a group of American representatives to go to France to verify and adopt the metric system.

Also, because of political tensions between the U.S. and France following the Revolutionary War, France did not invite an American delegation among the foreign dignitaries to come to Paris and learn about the new metric system.

### U.S. weights and measures mirrored the Monroe Doctrine

Fast forward to 1821. A study during the administration of James Monroe found that the U.S. system was pretty much uniform and didn’t require any changes.

Also, there was not much confidence that France was stable enough after the demise of Napoleon Bonaparte to maintain the French commitment to the metric system.

The U.S. Congress voted to recognize the metric system in 1866 and sent delegates to an international conference in France.

World representatives signed the Treaty of the Meter and established an International Bureau of Weights and Measures near Paris as the central authority for international metric standards.

So, while the U.S. ratified the treaty, and the metric system is officially recognized, that recognition has still not translated into everyday popular use.

While political leaders and some scientists urged involuntary use of the metric system, there never was a popular consensus to go metric.

In 1971, things seemed about to change when a report by the U.S. National Bureau of Standards suggested that the U.S. transition to the metric system over a period of 10 years.

Congress passed the Metric Conversion Act in 1971 but abolished the 10-year deadline. It also made the conversion voluntary.

Schoolchildren across the country began studying the metric system seriously and a few companies converted to the metric system, but enthusiasm faded along with any practical movement to make the switch.

Acts of Congress in 1988 and 1992 promoted the metric system as “preferred” for United States commerce–and required federal agencies to use the metric system for procurement, grants, and related business activity.

However, those amendments continued to make conversion voluntary for private industry.

While the federal government has continued to help smaller businesses convert to the metric system, progress has been tepid and slow. That’s because:

- Adopting the metric system means converting everything from equipment plans, and parts to road signs and bathroom scales. All that would be costly and time-consuming.
- American stubbornness is at the root of resistance to change, especially when foreign governments are involved. Then there is the traditional American individualism and independence, which have always been a defining characteristic of the country.

**The biggest reason,** however, is that Congress has failed to make the system mandatory for the entire country.

Until that universal mandate becomes a reality, most Americans will continue to think in terms of pounds and inches instead of kilograms and meters.

### Progress so far in the U.S. adoption of the metric system

Estimates are that about 30 percent of American manufactured products have gone metric.

In fact, pharmaceutical manufacturers now only display their products in metric units.

But, while some industries and manufacturers display both U.S. and metric units together on their products, mostly the U.S. is still the sole non-third-world nation that has not made the metric system compulsory.