21 knots to miles per hour
24.17 mph
21 kn = 24.17 mph.
miles per hour
24.17mph
21 kn = 24.17 mph
In short
How many miles per hour is 21 knots?
21 kn = 24.17 mph. 1 knot = 1.150779 miles per hour, so the working is 21 × 1.150779 = 24.17.
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 knot = 1.150779 miles per hour 21 × 1.150779 = 24.17
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 (mph) | Off by |
|---|---|---|
| Whole number | 24 | −0.16637 |
| 1 decimal | 24.2 | +0.03363 |
| 2 decimals | 24.17 | +0.00363 |
Round trip: take 24.17 mph back the other way and you land on 21.0032 kn — a drift of 0.0032 kn. That gap is the rounding, not the conversion.
What 21 kn looks like
22 kn
A strong breeze, force 6 on the Beaufort scale, which is the point at which small craft warnings are usually issued.
Frequently asked questions
What is 21 knots in miles per hour?
21 knots is 24.17 miles per hour. 1 knot = 1.150779 miles per hour, so the working is 21 × 1.150779 = 24.17.
How accurate is 24.17 mph?
Rounding to 24.17 mph and converting straight back gives 21.0032 kn, a drift of 0.0032 kn 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
Knots to MPH Converter
Convert knots to miles per hour — boat speed, wind speed, and aviation.
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