Conversion Calculator

Convert between commonly used units of measurement using our conversion calculator. Easily convert units of angle, area, length, speed, temperature, time, volume, or weight.

How To Convert Units of Measurement

People often deal with metrics and values in various units of measurement. However, it’s enough to confuse anyone, so let’s demystify how to convert between different units of measure.

Unit conversion is the process of expressing a quantity measured in one unit as the equivalent kind of quantity in a different unit of measurement. More specifically, Unit conversion is a multi-step process that involves multiplication or division by a numerical factor, selection of the correct number of significant digits, and rounding.^[1]

Let’s break down the conversion process into four simple steps.

Step One: Identify the Starting Unit

The first step in the conversion is to identify the starting unit of measure. This is the unit that describes the quantity you have.

For example, if you have a measurement of three feet, then feet are the starting unit of measure.

Step Two: Identify the Resulting Unit

The second step is to identify the resulting unit of measure, which is the unit you want to convert your measurement to.

Keep in mind that the resulting unit should measure the same quantity. For example, if your starting unit is expressed in a unit of length, the resulting unit should also be a unit of length.

Step Three: Find the Conversion Factor

The third step in the conversion process is to find the conversion factor between the starting and resulting units. You can use the table below, our comprehensive set of conversion calculators, or you can use a published reference, such as the one published by the National Institute of Standards and Technology.^[2]

Step Four: Do the Math to Convert

The fourth and final step to complete the conversion is to do the math using the conversion factor. The conversion factor might require you to multiply or divide the starting measurement by the factor, depending on how the factor is published.

If you have a conversion factor from the starting unit to the resulting unit, then you should multiply the starting measurement by the conversion factor to convert.

On the other hand, if you have a conversion factor from the resulting unit to the starting unit, then you’ll need to divide the starting measurement by the conversion factor to convert it.

Converting Between U.S. Customary And Metric Units

Many measurements in the United States use U.S. customary units of measurement, which have roots in the old imperial systems of the British. Measurements such as pounds, inches, and gallons are examples of U.S. customary units.

Throughout the rest of the world, many measurements are SI metric measurements. The international system of units (metric system) defines prefixes (kilo, milli, etc.) that may be used to express small or large numerical values in multiples of the base quantity.^[3]

One common challenge worldwide is converting between these two very different systems of measurement. The process to convert them, however, is the same as the one described above.

First, if the measurement uses a prefix to express a multiple, convert it to the base unit of measure. For instance, 10 centimeters should be converted to meters by dividing by 100 (centi is a multiple of 1/100 meter).

Then, use the conversion factor for meters to your resulting unit of measure and follow the four-step process outlined above.

Conversion Factors

The table below shows the conversion factors for the most commonly used units of area, length, speed, volume, and mass (weight).^[2]

Table showing conversion factors for common units of measurement.

Starting Unit	Resulting Unit	Conversion Factor
Area Units
square miles	square kilometers	2.589988
square feet	square meters	0.09290304
square feet	square inches	144
acres	square meters	4,046.873
Length Units
miles	kilometers	1.609344
yards	meters	0.9144
feet	meters	0.3048
feet	inches	12
inches	centimeters	2.54
inches	millimeters	25.4
Speed/Velocity Units
miles/hour	kilometers/hour	1.609344
feet/second	meters/second	0.3048
Volume Units
U.S. gallons	liters	3.785412
pints	liters	0.4731765
quarts	liters	0.9463529
fluid ounces	milliliters	29.57353
cubic feet	cubic meters	0.02831685
cubic inches	cubic centimeters	16.387064
Weight/Mass Units
long tons	kilograms	1,016.047
pounds	kilograms	0.45359237
pounds	ounces	16
ounces	grams	28.34952

Common Conversions

These are the conversions showing the equivalent values for commonly used units of measure.

Area Conversions

• 1 sq mi = 640 acres = 2.59 sq km
• 1 acre = 43,560 sq ft = 4047 sq m
• 1 sq ft = 0.093 sq m
• 1 sq km = 1,000,000 sq m = 247.1 acres

Length Conversions

• 1 mi = 5,280 ft = 1.609 km
• 1 ft = 12 in = 0.305 m = 30.48 cm
• 1 in = 2.54 cm = 25.4 mm
• 1 km = 1,000 m = 0.621 mi
• 1 m = 39.37 in = 0.3281 ft
• 1 cm = 10 mm = 0.394 in
• 1 mm = 0.0394 in

Volume Conversions

• 1 U.S. gallon = 4 quarts = 8 pints = 3.785 liters
• 1 liter = 2.113 pints = 1.057 quarts = 0.264 U.S. gallons

Weight/Mass Conversions

• 1 ton = 2,000 lb = 907.1847 kg
• 1 lb = 16 oz = 453.592 g
• 1 oz = 28.3495 g
• 1 kg = 1,000 g = 1,000,000 mg = 2.20462 lb

Other Conversion Calculators