Knots to MPH Converter

One knot is one nautical mile per hour — convert to mph, km/h and m/s for sailing, flying and wind forecasts.

Conversion table

Speed	In mph
1	1.1508 mph
2	2.3016 mph
3	3.4523 mph
4	4.6031 mph
5	5.7539 mph
10	11.5078 mph
15	17.2617 mph
20	23.0156 mph
25	28.7695 mph
30	34.5234 mph
40	46.0311 mph
50	57.5389 mph
60	69.0467 mph
70	80.5545 mph
75	86.3084 mph

🧭 The numbers that matter

1 knot1.1508 mph
1 knot1.852 km/h
10 knots11.51 mph
64 knots74 mph (Cat 1)

Talking about speed at sea

There is no such thing as "knots per hour". A knot already contains the hour: it is one nautical mile per hour, so saying it twice is like saying miles per hour per hour.
For a fast mental estimate, add 15% to knots to get mph, and add 85% to get km/h. Ten knots is roughly 11.5 mph or 18.5 km/h.
A nautical mile is longer than a statute mile: 1,852 m against 1,609 m. That is why the same distance is a smaller number in nautical miles.
Marine forecasts quote sustained wind in knots and gusts separately; the gust is what tears a sail, so never convert only the average.

Why a knot is a nautical mile per hour

The nautical mile is defined as exactly 1,852 metres, and that number is not arbitrary: it is very close to one minute of arc of latitude on the Earth's surface. Sixty nautical miles therefore make one degree of latitude, so a navigator can step off distance on a chart with the same dividers used to read position, without any conversion at all. A knot is simply one of those miles covered in an hour, which puts speed and chart distance in the same family of units. Against land measures: 1 knot = 1.1508 mph = 1.852 km/h = 0.5144 m/s.

The rope that gave the unit its name

Before instruments, speed was measured with a chip log: a weighted wooden quadrant thrown over the stern on a line with knots tied at regular intervals. The line ran out freely while a sandglass emptied, and the crew counted the knots that passed through their hands. Divide the knot spacing by the glass interval and you get a speed directly in nautical miles per hour, which is why the unit is named after a piece of rope rather than after a distance. The method survived for centuries because it needed no clock, no chart and no arithmetic.

Wind speeds worth recognising

Force 4, a moderate breeze: 11–16 knots, or 13–18 mph. Comfortable sailing, small waves with whitecaps.
Force 6, a strong breeze: 22–27 knots. Most small craft advisories start here.
Force 8, a gale: 34–40 knots, or 39–46 mph. This is the threshold that closes ports to small vessels.
Tropical storm: sustained 34–63 knots. Hurricane strength begins at 64 knots, which is 74 mph.
Category 5 on the Saffir-Simpson scale: 137 knots or more, about 157 mph.
Aviation crosswind limits for airliners are usually quoted between 25 and 38 knots depending on the type and the runway condition.

Who still measures in knots

Shipping and sailing, for both boat speed and current. A cruising yacht sails at 5–8 knots; a container ship at 18–24.
Aviation, worldwide. Airspeed, groundspeed and wind are all in knots, and altitude in feet — one of the few places where imperial and metric coexist by treaty.
Marine and aviation weather forecasts, including hurricane advisories from the National Hurricane Center.
Ocean currents. The Gulf Stream runs at up to about 4 knots at its core.
Sailing records: the outright windsurfing and kite records sit above 50 knots, roughly 58 mph.
Some navies and coast guards use knots for everything, including patrol vehicle speed on the water.

Worked examples

From a forecast to a number you can picture

A forecast says 25 knots

25 × 1.15078 = 28.8 mph
25 × 1.852 = 46.3 km/h
25 × 0.514444 = 12.9 m/s

25 knots = 28.8 mph = 46.3 km/h

A boat log reads 6.5 knots

6.5 × 1.15078 = 7.5 mph
In an eight-hour day: 6.5 × 8 = 52 nautical miles
52 nautical miles = 59.8 statute miles = 96.3 km

6.5 knots = 7.5 mph, or 52 nmi a day

Frequently Asked Questions

How many mph is 1 knot?

1.15078 mph. The relationship is exact by definition: one knot is one nautical mile of 1,852 metres per hour, and a statute mile is 1,609.344 metres, so the ratio is 1852 ÷ 1609.344. For a quick estimate, add about 15% to the knot figure.

Why do ships and planes use knots instead of mph?

Because the nautical mile matches the chart. One nautical mile is almost exactly one minute of latitude, so sixty of them make one degree, and a navigator can measure distance on a chart with the latitude scale printed down its side. Speed in nautical miles per hour keeps the whole calculation inside the same system — and aviation kept it worldwide for compatibility.

Is a nautical mile longer than a regular mile?

Yes, by about 15%. A nautical mile is 1,852 metres and a statute mile is 1,609.344 metres. So a 100-nautical-mile passage is 115 statute miles, and any speed in knots is a bigger real speed than the same number in mph.

Is it correct to say "knots per hour"?

No. The hour is already inside the unit — a knot is one nautical mile per hour. "Knots per hour" would describe acceleration, not speed. The phrase is common in films and headlines, but on a boat or in a cockpit it marks you out immediately.

What wind speed is a hurricane in knots?

Sixty-four knots of sustained wind, which is 74 mph or 119 km/h, is where the Saffir-Simpson scale begins at Category 1. Below that, 34 to 63 knots is a tropical storm. Category 5 starts at 137 knots, about 157 mph.

How do I convert knots to km/h quickly?

Multiply by 1.852, or in your head add 85%: double the number and take off a bit. Twenty knots is close to 37 km/h. Going the other way, divide km/h by 1.852, or halve and add a tenth as a rough check.