The United States is the only country besides Myanmar and Liberia that does not use the metric system as its official system of measurements. Rather, it uses its own system called the U.S. customary system. This system is a derivative of the Imperial System, which was used by Britain until the 20th century. Whereas metric countries use units such as meters, grams, metric tons, Celsius temperature readings, liters and hectares, the U.S. system uses inches, feet, yards, miles, ounces, pounds, Fahrenheit temperature readings and acres. Here are some common conversions.

U.S. System vs. Metric System: Length Conversions

1 inch = 2.54 centimeters 1 foot = 0.3048 meters 1 yard = 0.91 meters 1 mile = 1.61 kilometers

U.S. Customary vs. Metric System: Weight Conversions

1 ounce = 28.35 grams 1 pound = 0.45 kilograms 1 US ton = 0.91 metric tons

U.S. Customary vs. Metric System: Temperature Conversions

When converting temperatures, remember these formulas:

C = (F - 32) / 1.8 F = (C x 1.8) + 32

Where: C = Celsius F = Fahrenheit

U.S. Customary vs. Metric System: Area and Volume Conversions

Area Conversions: 1 acre = 0.40 hectares 1 square inch = 6.45 square centimeters 1 square foot = 0.09 square meters 1 square yard = 0.84 square meters 1 square mile = 2.60 square kilometers

Volume Conversions: 1 teaspoon = 4.93 milliliters 1 tablespoon = 14.79 milliliters 1 fluid ounce = 29.57 milliliters 1 pint = 0.47 liters 1 quart = 0.95 liters 1 gallon = 3.79 liters

Why the Metric System Is Easier to Use

Unlike the U.S. Customary system, conversions between metric system units are easy and precise because they are based on the decimal system. For example, if you want to convert kilometers to meters, you simply multiply the kilometers by 1,000. However, if you want to convert miles to feet, you have to multiply the number of miles by 5,280. This is clearly a more difficult calculation.

Why Haven't We Converted to Metric?

Many people wonder why we are the only Western country still using such a complicated system for measurement. The main reason is because our system has been in place for such a long time that people have gotten used to it. Back in the 1970s, there was a movement to change to the metric system. For example, cereal boxes included their metric weights. The government even had a plan to officially make the switch to metric. However, the plan was never carried out, mainly due to concerns about people resisting the big change. The U.S. customary system may be here to stay.