The factor, and a shortcut
A knot is one nautical mile per hour, which works out to 1.15078 mph. To convert in your head, add about 15%: 20 kt → 20 + 3 = 23 mph (exact 23.0). In metric it is even cleaner — 1 knot is exactly 1.852 km/h, because the nautical mile is defined as 1852 metres.
Why a knot is faster than a land mile per hour
The two units differ because the mile underneath them is a different length. A nautical mile is one minute of latitude on the globe; a statute mile is the old land measure. Same number, different distance covered.
A nautical mile is about 15% longer, so any speed in knots is 15% higher when written as mph.
Wind and aircraft speeds
| Knots | mph | km/h | Context |
|---|---|---|---|
| 10 kt | 11.5 | 18.5 | Moderate breeze |
| 20 kt | 23.0 | 37.0 | Strong breeze |
| 34 kt | 39.1 | 63.0 | Gale |
| 64 kt | 73.6 | 118.5 | Hurricane, Cat 1 |
| 137 kt | 157.6 | 253.7 | Hurricane, Cat 5 |
| 250 kt | 287.7 | 463.0 | Boeing 737 cruise |
| 460 kt | 529.4 | 852.0 | Boeing 787 cruise |
A knot measures speed, not distance. "A trip of 100 knots" is wrong; it is either "100 nautical miles" or "a speed of 100 knots."
Common questions
How fast is 1 knot in mph?
One knot is 1.15078 mph. A knot is about 15 percent faster than a land mile per hour because a nautical mile (1852 m) is longer than a statute mile (1609 m).
Why do ships and planes use knots instead of mph?
One knot is one nautical mile per hour, and one nautical mile equals one minute of latitude. That lets a navigator read distance straight off a chart: 60 nautical miles is one degree of latitude. Switching to mph would break that link.
How many knots is a hurricane?
A hurricane starts at 64 knots, which is 74 mph or 119 km/h (Category 1). The strongest, Category 5, is 137 knots or more, about 157 mph.
