A knot is a speed of one nautical mile per hour, and because a nautical mile is based on the circumference of the Earth it is slightly longer than a statute mile. This converter handles knots, miles per hour, kilometres per hour and the two SI speed units, which covers most of what you need at sea, in the air or on the road.
What Is the Knots to MPH Calculator?
One knot is one nautical mile per hour. A nautical mile is defined as one minute of arc along a great circle on the Earth, which works out at 1,852 metres, so a knot is 1.852 kilometres per hour or about 1.15078 miles per hour.
Because the nautical mile is tied to the Earth rather than to a survey, a knot is a natural unit for both navigation and airspeed. The calculator converts to and from every speed unit you are likely to meet.
How the Conversion Works
1 knot = 1.852 km/h = 1.15078 mph = 0.514444 m/s = 1.68781 ft/s
The definition is fixed by the 1929 international agreement that set the nautical mile at exactly 1,852 metres, which replaced the older British Admiralty figure of 1,853.18 metres.
Working in the other direction, multiply miles per hour by 0.868976 to get knots. The factor is less than one, so 100 miles per hour is 86.9 knots.
Where Knots Are Used
Sailing is measured in knots, and so is a ship’s speed over the ground. Modern GPS units will happily display either scale, but the traditional practice at sea is knots.
Aviation uses knots too, although only for the true airspeed of light aircraft. Above about 20,000 feet, indicated airspeed no longer matches true airspeed, because the air is thinner and the pitot tube under-reads. That is why a jet on the flight deck will be talking about hundreds of knots while the airliner’s instruments show a much lower figure.
Practical Points
The knot is also a useful unit for fuel planning, because a nautical mile is historically one minute of steaming. A vessel making 10 knots covers 10 nautical miles in an hour, which makes fuel per nautical mile a natural figure for a passage plan.
Remember the 60 to 15 rule for manoeuvring speed in a seaway. 6 knots gives you six boat lengths of distance to stop and six minutes of time, and 2 knots gives you two boat lengths and two minutes.
Frequently Asked Questions
How many mph is 10 knots?
About 11.5 miles per hour, since one knot equals 1.15078 miles per hour. Ten knots is also 18.52 kilometres per hour, which is roughly 11.5 miles per hour.
Why is a knot not the same as a mile per hour?
A nautical mile is 1,852 metres, based on one minute of arc of the Earth’s circle, while a statute mile is 1,609.344 metres. The nautical mile is about 15 percent longer, so a knot is about 15 percent faster than a mile per hour.
How fast is 20 knots in miles per hour?
23.02 miles per hour, or 37.04 kilometres per hour. Twenty knots is a common cruising speed for a medium sized motorboat and a typical speed for a light aircraft.
What speed is 100 knots in miles per hour?
115.08 miles per hour, which is also 185.2 kilometres per hour or 51.4 metres per second. The conversion factor from knots to miles per hour is 1.15078.
Is a knot the same as a nautical mile per hour?
Yes, exactly. The knot is defined as one nautical mile per hour, and it is a speed unit rather than a distance unit. It is occasionally confused with the nautical mile itself, which is a distance of 1,852 metres.