21 miles to kilometers
33.80 km
21 mi = 33.80 km.
kilometers
33.80km
21 mi = 33.80 km
The short answer
How many kilometers is 21 miles?
21 mi = 33.80 km. 1 mile = 1.609344 kilometers, so the working is 21 × 1.609344 = 33.80.
The working
The factor below is an exact definition rather than a measurement, so nothing is approximated in the arithmetic. The only rounding on this page happens where a number is displayed.
1 mile = 1.609344 kilometers 21 × 1.609344 = 33.80
How much precision do you need?
Each row is the same answer cut at a different number of decimals, with what that choice costs you. Pick the shortest row whose error is smaller than whatever you are measuring with.
| Rounded to | Answer (km) | Off by |
|---|---|---|
| Whole number | 34 | +0.20378 |
| 1 decimal | 33.8 | +0.00378 |
| 2 decimals | 33.80 | +0.00378 |
Round trip: take 33.80 km back the other way and you land on 21.0023 mi — a drift of 0.0023 mi. That gap is the rounding, not the conversion.
What 21 mi looks like
21 mi
The Strait of Dover, the narrowest crossing of the English Channel, is about 20.7 miles wide.
Frequently asked questions
What is 21 miles in kilometers?
21 miles is 33.80 kilometers. 1 mile = 1.609344 kilometers, so the working is 21 × 1.609344 = 33.80.
How accurate is 33.80 km?
Rounding to 33.80 km and converting straight back gives 21.0023 mi, a drift of 0.0023 mi from the 21 you started with. The factor itself is exact; every bit of that difference comes from the rounding, not the conversion.
Nearby values
Any value at all
Miles to Km Converter
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