Convert 21 miles to kilometers

Precise decimal and fraction answers

The conversion in kilometers rounded to six significant decimal places is 21 mi = 33.796224 km. The precise fraction answer is 33 ¹²²³/₁₅₃₆ km.

How many kilometers are in a mile?

There are 1.609 kilometers in one mile. A mile is 1.609 times longer than a kilometer. A kilometer is 62.14% of a mile

Miles to kilometers conversion factor and formulas

The conversion factor between miles and kilometers is 1.609. This represents the ratio of kilometers per one mile. To calculate the value in kilometers, we can either multiply by the conversion factor or divide by its inverse.

Multiplication

To convert from miles to kilometers, multiply miles by 1.609.
The formula is expressed as:
mi × 1.609 = km

Division

Alternatively we can divide by the inverse conversion factor to get the same result.
The inverse of 1.609 is 1/1.609 or 0.621. To convert from miles to kilometers, divide miles by 0.621.
The formula is expressed as:
mi ÷ 0.621 = km

To convert 21 miles to kilometers, multiply 21 miles by 1.609.
21 mi × 1.609 = 33.796 km

How long are 21 miles?

Real world scale examples to visualize the length of 21 miles / 33.796 kilometers

• The same width of the English Channel (21 mi)
• 79% of the length of a marathon race (26.6 mi)
• 10% of the distance from London to Paris (214 mi)

About this conversion

Converting miles to kilometers is a conversion between units from separate unit systems - miles are US Customary / UK Imperial defined units while kilometers are metric (SI) .

About Miles

The mile is a measure of distance between two points used within the US Customary and British Imperial units of measure. It is customarily used to measure large geographical distances. The mile is officially defined as 5,280 feet, 1,760 yards or 1,609.344 meters. The abbreviation or for miles is 'mi' or sometimes 'm' as in miles per hour. The mile's origin stems from the Roman mile, which marked the distance the Roman army could march over 1,000 (mille) paces.

About Kilometers

Within the SI (metric) system of measurement, the kilometer is officially defined as being equal to 1,000 meters. It is commonly used as measurement for geographic distances in similar circumstances where a mile would be used in the U.S. Internationally it is spelled 'kilometre' whereas the U.S. spells it 'kilometer'. The symbol for a kilometer is km however k is sometimes used.

Reverse this conversion

Convert from kilometers to miles instead.

References and Citations

1. National Institute of Standards and Technology (NIST) General Tables of Units of Measurement
2. International Bureau of Weights and Measures (BIPM) The International System of Units (SI)