18 knots to miles per hour
20.71 mph
18 kn = 20.71 mph.
miles per hour
20.71mph
18 kn = 20.71 mph
In short
How many miles per hour is 18 knots?
18 kn = 20.71 mph. 1 knot = 1.150779 miles per hour, so the working is 18 × 1.150779 = 20.71.
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 18 × 1.150779 = 20.71
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 | 21 | +0.28597 |
| 1 decimal | 20.7 | −0.01403 |
| 2 decimals | 20.71 | −0.00403 |
Round trip: take 20.71 mph back the other way and you land on 17.9965 kn — a drift of 0.0035 kn. That gap is the rounding, not the conversion.
Frequently asked questions
What is 18 knots in miles per hour?
18 knots is 20.71 miles per hour. 1 knot = 1.150779 miles per hour, so the working is 18 × 1.150779 = 20.71.
How accurate is 20.71 mph?
Rounding to 20.71 mph and converting straight back gives 17.9965 kn, a drift of 0.0035 kn from the 18 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.
Open the knots to MPH converter →