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.
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On this page:
- Conversion Calculator
- How To Convert Units of Measurement
- Step One: Identify the Starting Unit
- Step Two: Identify the Resulting Unit
- Step Three: Find the Conversion Factor
- Step Four: Do the Math to Convert
- Converting Between U.S. Customary And Metric Units
- Conversion Factors
- Common Conversions
- Other Conversion Calculators
- References
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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.
For example, let’s say you want to convert 3 feet from feet to inches. If you look up the conversion factor, you’ll find that 1 foot equals 12 inches.
In this case, you multiply the starting measurement of 3 feet by the conversion factor of 12 inches to convert.
3 ft × 12 in = 36 in
Thus, 3 feet is equal to 36 inches.
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.
For example, let’s say you want to convert 24 inches from inches to feet. Recall the conversion factor from above: 1 foot equals 12 inches.
Given that the units of measure in the conversion factor are reversed, you’ll need to divide the starting measurement of 24 inches by the conversion factor of 12 inches to convert back to feet.
24 in ÷ 12 in = 2 ft
Thus, 24 inches is equal to 2 feet.
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]
| 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
References
- National Institute of Standards and Technology, Unit Conversion, https://www.nist.gov/pml/owm/metric-si/unit-conversion
- National Institute of Standards and Technology, The International System of Units (SI) – Conversion Factors for General Use, https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication1038.pdf
- Ambler Thompson and Barry N. Taylor, Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology, https://physics.nist.gov/cuu/pdf/sp811.pdf