Length, Area, & Volume Conversions

Scientists, tradesmen, builders, and surveyors use a plethora of units to measure length, area, and volume. When the need arises to convert between different systems of measurement, you can either use conversion tables or conversion calculators, such as those below.

In the first line, enter the quantity and unit of your data. In the next line, select the unit you want to convert to.

The units within a particular system of measurement are often multiples of each other. For instance, in the metric system, units vary by powers of 10. A kilometer is 1000 meters, a centimeter is 1/100 of a meter, a liter is 1000 cubic centimeters, etc.

In the US system of measures, the units increase and decrease by multiples of 2 and 3. For example, there are 6 picas in an inch, 12 inches to a foot, and 3 feet to a yard. Most of the customary measures for food volume vary by powers of 2: 16 tablespoons in a cup, 4 cups in a quart, and 4 quarts in a gallon. There are some curious exceptions; notably, a gallon is defined as exactly 231 cubic inches.

US measures have been standardized so that they correspond to exact values in the metric system, which makes conversions simpler and more precise. Starting from the fact that 1 cm is equivalent to 2.54 inches, you can obtain almost all of the other conversions.

Although the UK uses the metric system, they still retain several Imperial units. Most of these are the same as their US counterparts. For instance, pounds and ounces, and feet and inches are equivalent on both sides of the pond. Some are different, such as gallons. An Imperial gallon is about 20% larger than a US gallon.

Sample Calculations

To convert between units using values from a conversion chart, you simply multiply by the conversion factor. For example, the conversion factor for miles to kilometers is 1.609344, which means there are 1.609344 km per mile. So if you need to convert 5.8 miles to kilometers, you compute (5.8)(1.609344) = 9.33 km.

Conversion factors in opposite directions are reciprocals of one another. For instance, the number for Kilometers to miles is 0.621371192237334, which means there are about 0.62137 miles in a km. To convert 783 km to miles, you compute (783)(0.62137) = 486.53 miles.

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