Knots to mph
1 knot = 1.15078 mph = 1.852 km/h
Type a speed in knots to get miles per hour. Use the swap button to convert mph to knots. Need km/h, m/s or Mach too? Try the all-in-one speed converter.
Formula: mph = kn × 1.150779
Knots to mph formula
A knot is one nautical mile per hour. Since one nautical mile is 1,852 meters and one statute mile is 1,609.344 meters:
mph = knots × 1.15078
km/h = knots × 1.852
knots = mph × 0.868976
Example: a sailboat doing 7 knots is moving at 7 × 1.15078 = 8.06 mph, or 7 × 1.852 = 12.96 km/h.
Quick mental math: add about 15% to get mph (30 knots ≈ 30 + 4.5 = 34.5 mph), or nearly double it to get km/h (30 knots ≈ 55.6 km/h).
What is a knot?
A knot (symbol kn or kt) is a speed of one nautical mile per hour. The nautical mile was set at exactly 1,852 meters by international agreement in 1929. It was originally tied to one minute of latitude, which is why navigators, who work with latitude and longitude, still prefer it.
The name comes from the old “chip log”: sailors threw a weighted wooden board overboard on a line with knots tied at regular intervals and counted how many knots ran out in a fixed time. That count was the ship’s speed in knots — and the word stuck.
Note that “knots per hour” is incorrect: a knot already means “per hour”. Saying a ship travels at “20 knots” is the same as “20 nautical miles per hour”.
Where knots are used
- Boating and shipping. Boat speeds, currents and voyage plans are given in knots worldwide.
- Aviation. Pilots and air traffic control use knots for airspeed and ground speed, and nautical miles for distance.
- Weather. Marine forecasts and airport weather reports give wind speed in knots. The Beaufort scale and storm warnings are often quoted in knots too.
On the water, a GPS speedometer is the easiest way to read your speed in knots. Open the online speedometer, tap kn, and your phone will show your speed over ground.
Knots to mph and km/h conversion table
| Knots | mph | km/h | m/s |
|---|---|---|---|
| 1 kn | 1.15 mph | 1.85 km/h | 0.51 m/s |
| 2 kn | 2.3 mph | 3.7 km/h | 1.03 m/s |
| 3 kn | 3.45 mph | 5.56 km/h | 1.54 m/s |
| 4 kn | 4.6 mph | 7.41 km/h | 2.06 m/s |
| 5 kn | 5.75 mph | 9.26 km/h | 2.57 m/s |
| 6 kn | 6.9 mph | 11.11 km/h | 3.09 m/s |
| 7 kn | 8.06 mph | 12.96 km/h | 3.6 m/s |
| 8 kn | 9.21 mph | 14.82 km/h | 4.12 m/s |
| 9 kn | 10.36 mph | 16.67 km/h | 4.63 m/s |
| 10 kn | 11.51 mph | 18.52 km/h | 5.14 m/s |
| 15 kn | 17.26 mph | 27.78 km/h | 7.72 m/s |
| 20 kn | 23.02 mph | 37.04 km/h | 10.29 m/s |
| 21 kn | 24.17 mph | 38.89 km/h | 10.8 m/s |
| 25 kn | 28.77 mph | 46.3 km/h | 12.86 m/s |
| 26 kn | 29.92 mph | 48.15 km/h | 13.38 m/s |
| 30 kn | 34.52 mph | 55.56 km/h | 15.43 m/s |
| 35 kn | 40.28 mph | 64.82 km/h | 18.01 m/s |
| 40 kn | 46.03 mph | 74.08 km/h | 20.58 m/s |
| 45 kn | 51.79 mph | 83.34 km/h | 23.15 m/s |
| 50 kn | 57.54 mph | 92.6 km/h | 25.72 m/s |
| 55 kn | 63.29 mph | 101.86 km/h | 28.29 m/s |
| 60 kn | 69.05 mph | 111.12 km/h | 30.87 m/s |
| 70 kn | 80.55 mph | 129.64 km/h | 36.01 m/s |
| 80 kn | 92.06 mph | 148.16 km/h | 41.16 m/s |
| 90 kn | 103.57 mph | 166.68 km/h | 46.3 m/s |
| 100 kn | 115.08 mph | 185.2 km/h | 51.44 m/s |
| 105 kn | 120.83 mph | 194.46 km/h | 54.02 m/s |
| 115 kn | 132.34 mph | 212.98 km/h | 59.16 m/s |
| 120 kn | 138.09 mph | 222.24 km/h | 61.73 m/s |
| 150 kn | 172.62 mph | 277.8 km/h | 77.17 m/s |
| 200 kn | 230.16 mph | 370.4 km/h | 102.89 m/s |
| 250 kn | 287.69 mph | 463 km/h | 128.61 m/s |
| 300 kn | 345.23 mph | 555.6 km/h | 154.33 m/s |
| 400 kn | 460.31 mph | 740.8 km/h | 205.78 m/s |
| 500 kn | 575.39 mph | 926 km/h | 257.22 m/s |
Typical speeds in knots
| What | Knots | mph |
|---|---|---|
| Cruising sailboat | about 5–8 kn | 6–9 mph |
| Large container ship | about 16–24 kn | 18–28 mph |
| Recreational powerboat | often 20–40 kn | 23–46 mph |
| Gale-force wind | 34–47 kn | 39–54 mph |
| Hurricane-force wind | 64 kn and above | 74 mph and above |
| Small single-engine plane (cruise) | about 110–125 kn | 127–144 mph |
| Airliner at cruising altitude | about 450–500 kn | 518–575 mph |
Typical values vary with the vessel, aircraft and conditions. Aircraft speeds are true airspeed at cruising altitude; ground speed changes with the wind.
Knots vs mph vs km/h
All three measure the same thing — distance per hour — with different distance units. One knot (1.151 mph) is a bit faster than one mile per hour, and one mile per hour (1.609 km/h) is faster than one kilometer per hour. In everyday use:
- mph is used for road speeds in the US and UK — see mph to km/h;
- km/h is used for road speeds almost everywhere else — see km/h to mph;
- knots are used at sea, in the air and in marine weather.
Frequently asked questions
How many mph is 1 knot?
1 knot equals 1.15078 mph (about 1.15 mph) and exactly 1.852 km/h. A knot is one nautical mile per hour.
How do I convert knots to mph?
Multiply the speed in knots by 1.15078. For example, 20 knots × 1.15078 = 23.02 mph. For a quick estimate, add 15%: 20 + 3 = 23 mph.
How many mph is 21 knots?
21 knots is 24.17 mph, or 38.89 km/h.
How many mph is 40 knots?
40 knots is 46.03 mph (74.08 km/h). As a sustained wind, 40 knots is gale force.
Is a knot faster than a mile per hour?
Yes. A knot is about 15% faster than 1 mph, because a nautical mile (1,852 m) is longer than a statute mile (1,609.344 m).
What is the difference between a nautical mile and a mile?
A statute mile, used on roads in the US and UK, is 5,280 feet (1,609.344 m). A nautical mile is exactly 1,852 m — about 6,076 feet, or 1.15 statute miles. It was originally based on one minute of latitude, which makes it convenient for navigation with charts.
Why do ships and planes use knots?
Sea and air navigation measures distance in nautical miles because one nautical mile corresponds to roughly one minute of latitude on a chart. Measuring speed in nautical miles per hour (knots) keeps distance, speed and time calculations simple.
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