Convert knots to km/h knots ↔ kilometres per hour Free Online Secure
Type a value in knots and read it in kilometres per hour at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Convert to kilometres per hour
Common values — Convert knots to km/h (knots ↔ kilometres per hour)
| kn | km/h |
|---|---|
| 1 | 1.852 |
| 2 | 3.704 |
| 3 | 5.556 |
| 5 | 9.26 |
| 10 | 18.52 |
| 20 | 37.04 |
| 50 | 92.6 |
| 100 | 185.2 |
Where these units come from
Speed has no unit of its own: it is a length divided by a time, so every trade simply kept the length it was already using. That is why the same motion is 100 km/h on a European road sign, 62 mph on an American one and 27.8 m/s in a physics problem. The knot is the oldest of them and the most literal: sailors paid out a line with knots tied at even spacing and counted how many ran through their fingers while a sand glass emptied, so the speed was read off in knots. One knot is one nautical mile per hour, and a nautical mile is a minute of latitude — which is why ships and aircraft still use it. The speed of light is the odd one out: since 1983 it is not measured but fixed at exactly 299,792,458 m/s, because the metre is now defined from it.
Where you meet them
Kilometres and miles per hour live on speedometers and road signs, metres per second in physics, engineering and wind reports, feet per second in ballistics and in American machine shops. Knots carry shipping, aviation and marine weather, and Mach numbers appear wherever an aircraft is fast enough for the air's own stiffness to matter. The speed of light turns up less in daily life than in distances: a light year is simply how far it gets in one.
Questions people ask
Is Mach 1 a fixed speed?
No. Mach is a ratio to the speed of sound in the surrounding air, and sound travels more slowly in colder air. This page uses the standard sea-level figure, 340.294 m/s, so Mach 1 here is about 1225 km/h. At the altitude airliners cruise at, the air is some 50 degrees colder and the same Mach 1 is roughly a tenth slower. An aircraft can therefore hold a constant Mach number while its speed over the ground changes.
Why do ships and aircraft use knots rather than km/h?
Because a nautical mile is one minute of arc of latitude. A vessel making one knot covers one minute of latitude in an hour, so speed, time and position on a chart fit together without conversion. The same reasoning kept the nautical mile at exactly 1852 metres rather than rounding it to something tidier.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
Ocean racing and sailing records: from knots to km/h
The skipper of an ocean racer talks about 30 knots of boat speed. A flying catamaran touches 50. A cruising couple counts a good day as 120 nautical miles at 5 knots. Sailing lives in knots, but spectators, journalists and non-sailing relatives think in kilometres per hour. To convert knots to km/h, multiply by 1.852: 10 knots is 18.5 km/h, 30 knots is 55.6 km/h and 50 knots is 92.6 km/h. The calculator above multiplies as you type, and the sections below put the figures into the world of racing, cruising and records.
You will find the rule with worked examples, a short profile of each unit, a comparison, a long set of cases from sailing and the slips to avoid. The arithmetic runs in your browser, and what you type is not sent anywhere. For navigation, always rely on official charts and instruments.
How to convert knots to km/h: multiply by 1.852
The rule
A knot is one nautical mile per hour, and a nautical mile is exactly 1,852 metres. To convert knots to km/h, multiply the number of knots by 1.852. So 6 knots is 11.1 km/h, 15 knots is 27.8 km/h and 40 knots is 74.1 km/h. To go back, multiply by 0.54.
Worked examples
A cruising sailboat at 6 knots does 11.1 km/h. A racing monohull at 25 knots does 46.3 km/h. A flying catamaran at 45 knots does 83.3 km/h, and a record kiteboarder at 58 knots does 107.4 km/h.
Why 1.852
The nautical mile was based on one minute of latitude, and today it is fixed at 1,852 metres. The factor is exact, so no rounding enters the conversion. A quick estimate is to double the knots and take off about 7 per cent.
A quick sanity test
The km/h figure is always 85 per cent bigger than the knots figure. If a “convert knots to km/h” calculation result is smaller than the starting number, you used 0.54 instead.
The knot
The unit of the sea
The knot is a nautical mile per hour. The name comes from the knotted line paid out from a ship to measure speed through the water. Ships, aircraft and sailors use it, and it appears on every marine instrument.
Where it appears
Boat instruments, race reports, marine forecasts and charts.
The kilometre per hour
The unit of the shore
The kilometre per hour is the unit of road, rail and everyday life ashore. When a sailing story is told to a general audience, km/h helps people compare a boat with a car or a bike.
Where it appears
News reports, television commentary and magazine features.
Knots against kilometres per hour
One knot is 1.852 km/h. A boat doing 20 knots covers 37 kilometres in an hour, and 480 nautical miles in a day is 889 km. Sailors compare speeds across oceans in knots, while a journalist writing about the record for a land audience wants 37 or 40 km/h. Both describe the same performance.
The factor is exact, so no rounding enters. The only trap is direction: from knots to km/h the number grows.
Where the conversion shows up
Cruising
A cruising sailboat averages 5 to 6 knots, which is 9.3 to 11.1 km/h, over a day, covering 120 to 150 nautical miles, or 222 to 278 km. The Atlantic Rally for Cruisers sails about 2,700 nautical miles, or 5,000 km, in 15 to 20 days, an average of 6 to 7.5 knots. A “convert knots to km/h” calculation translates the log for relatives at home.
Offshore racing
The Sydney to Hobart race covers 628 nautical miles, or 1,163 km. The record is 1 day, 9 hours and 15 minutes, an average of 18.9 knots, which is 35 km/h. A typical yacht takes three days, an average of 8.7 knots, or 16 km/h. The Vendée Globe fleet averages about 16 knots, which is 30 km/h, over 74 to 80 days alone.
Foiling
The foiling AC75 boats of the America's Cup reach over 50 knots, which is 92.6 km/h, in 20 knots of wind. SailGP F50 catamarans pass 50 knots too. Hydrofoils lift the hulls out of the water, removing most drag, so the speeds exceed the wind speed several times over. At such speeds the boat moves faster than most cars in a city.
Hull speed
The hull speed of a displacement boat is about 1.34 times the square root of its waterline length in feet. A 30-foot waterline gives 7.3 knots, or 13.5 km/h, a 40-foot gives 8.5 knots, or 15.7 km/h, and a 50-foot gives 9.5 knots, or 17.6 km/h. Above this, the wave pattern holds the boat back, unless it planes or foils. Designers state the figure in knots, and a “convert knots to km/h” calculation helps in conversation ashore.
Ships and ferries
Big container ships do 20 to 24 knots, or 37 to 44 km/h. A cruise ship does 18 to 22 knots, or 33 to 41 km/h. A high-speed ferry reaches 35 to 40 knots, or 65 to 74 km/h. Tankers cruise at 13 to 16 knots, or 24 to 30 km/h. A conversion table in a port guide uses both units, since local drivers want km/h while captains read knots.
Aircraft airspeed
Pilots also use knots. A light aircraft cruises at 110 knots, which is 204 km/h, and a jet airliner at 450 knots, which is 833 km/h. Wind aloft is in knots too. A tailwind of 50 knots, or 93 km/h, turns a 450-knot airspeed into a ground speed of 500 knots, or 926 km/h. Navigation systems in boats and planes share the unit, so sailors who fly find the conversion natural.
Distance, time and speed
The three variables of sailing passage planning are connected by distance equals speed times time. For 90 nautical miles at 6 knots, the passage takes 15 hours. In km, 167 km at 11.1 km/h gives the same 15 hours. The unit pair must match: nautical miles with knots, or kilometres with km/h. Mixing them is a classic cause of late arrivals.
The sixty rule
A knot is a minute of latitude per hour. Sixty nautical miles equal one degree of latitude, which is 111 km. A sailor going north at 6 knots, or 11.1 km/h, changes latitude by one degree in ten hours. This rule gives a mental way to turn a latitude difference into a distance in nautical miles, and from there with a “convert knots to km/h” calculation into a time at a given speed.
Spreadsheet formulas
Place speeds in knots in column A and use =A2*1.852 in column B. For the reverse, use =B2/1.852. Add a column for the time of a passage, =distance_in_nm/A2. Label each column with its unit and use one decimal for the speeds.
Rounding and precision
The factor is exact: 12 knots is 22.224 km/h. A boat's log reads to a tenth of a knot, so 22.2 km/h is enough. Race reports give average speeds to one decimal, and the official results use elapsed time rather than speed. Round to the precision of the instrument.
A mental shortcut
Double the knots and subtract 7.4 per cent of the double. For 20 knots: 40 minus 3 gives 37 km/h. For 10 knots: 20 minus 1.5 gives 18.5. For 30 knots: 60 minus 4.4 gives 55.6. The shortcut is exact because 1.852 is 2 times 0.926.
Landmarks to memorise
5 knots is 9.3 km/h, 10 knots is 18.5 km/h, 15 knots is 27.8 km/h, 20 knots is 37 km/h, 30 knots is 55.6 km/h and 50 knots is 92.6 km/h. With these landmarks, you can place any sailing speed on a familiar scale.
Reference ladder
2 knots is 3.7 km/h. 6 knots is 11.1 km/h. 12 knots is 22.2 km/h. 18 knots is 33.3 km/h. 25 knots is 46.3 km/h. 40 knots is 74.1 km/h. 65 knots is 120.4 km/h. 100 knots is 185.2 km/h. A ladder like this makes a quick check easy.
Checking by reversing
To check any convert knots to km/h result, divide it by 1.852. If 20 knots became 37 km/h, then 37 divided by 1.852 is 20. A second test is the size: the km/h number should be almost twice the number of knots.
Wind and boat speed
A performance cruiser in 15 knots of wind, which is 27.8 km/h, sails at 7 to 8 knots, or 13 to 15 km/h, on a beam reach. A racing yacht can exceed the wind speed on a reach. Polar diagrams show the target speed for each wind angle and strength, always in knots, and crews learn to read them without conversion.
Relation to mph and m/s
One knot is 1.151 mph and 0.514 m/s. A speed of 20 knots is 23 mph and 10.3 m/s. American boaters on lakes use mph, those at sea knots, and scientists use m/s. A sailing log with the three units is common in research cruises.
Speed through water and over ground
The log measures speed through water, and GPS speed over ground. With a 2-knot current against you, 8 knots through the water is 6 knots over the ground, which is 11.1 km/h. Passage plans use speed over ground, because it decides when you arrive. Reporting a speed in km/h requires saying which of the two you mean.
Safety and speed
A man overboard at 8 knots, which is 14.8 km/h, drifts astern 4 metres each second. In a minute the boat is 247 m away. Fast boats such as foiling catamarans at 40 knots, or 74 km/h, are 1.2 kilometres away in a minute. Lifejackets and tethers are mandatory on racing yachts at these speeds, and a “convert knots to km/h” calculation makes the figures clear for crews of different nationalities.
Reading a race tracker
Online race trackers show boats with speed in knots, often with a toggle for km/h or mph. A flag at 21.5 knots means 39.8 km/h. Fans follow the fleet and compare, and the trackers update every few minutes. Knowing the conversion helps you to understand whether a surge at the front is real or a rounding of the data.
Sailing around a headland
Coastal passages are planned with tides, and a boat doing 6 knots, which is 11.1 km/h, can gain or lose hours. Rounding a headland with a 3-knot tide with you gives 9 knots over the ground, which is 16.7 km/h, and the same tide against drops it to 3 knots, which is 5.6 km/h. Skippers wait for the right tide, and a “convert knots to km/h” calculation helps visitors understand why.
Anchor watch and drift
A boat dragging its anchor at 0.5 knots, which is 0.9 km/h, moves 15 metres per minute. In a gale the drift can reach 1 or 2 knots, or 1.9 to 3.7 km/h. An anchor alarm on a phone sets a radius and warns if the boat leaves it. Understanding the speeds involved helps a crew react in time, especially at night.
Radar and collision avoidance
A radar plot shows other vessels' course and speed in knots. Two ships closing at a combined 30 knots, which is 55.6 km/h, with a gap of 6 nautical miles, or 11.1 km, meet in 12 minutes. Collision regulations give rules for action, and the closing speed in knots gives the time left to take it. Navigators convert to minutes using the sixty rule.
Navigating in fog
International regulations require a safe speed in poor visibility, one that allows the boat to stop within the distance it can see. In thick fog a small yacht may slow to 3 or 4 knots, which is 5.6 to 7.4 km/h. Ferries run to their schedules by relying on radar, but they too slow down. The choice is made by the master at the time.
Speed records under sail
The outright sailing speed record over 500 metres is about 65.45 knots, which is 121.2 km/h, set by a specially built craft. Kiteboarders have recorded roughly 58 knots, or 107 km/h, and windsurfers over 50 knots, or 93 km/h. These records are set on short, flat courses with steady wind. A “convert knots to km/h” calculation places them next to the speed of a motorway car.
Round the world
The Vendée Globe course is about 24,300 nautical miles, or 45,000 km. A fleet averaging 16 knots, which is 30 km/h, takes about 63 days, but the real winners take 74 to 80 because of calms and storms. Fully crewed maxi trimarans in the Jules Verne Trophy average over 25 knots, which is 46 km/h, and circle the globe in just over a month.
Distance in a day
A 24-hour run is the standard measure of fast sailing. 300 nautical miles, which is 556 km, is a very good run for a monohull cruiser racer, while the best ocean racing multihulls exceed 800 nautical miles, or 1,480 km. These are averages of 12.5 knots, which is 23 km/h, for the first and over 33 knots, which is 62 km/h, for the second.
Currents and tides
Tidal currents in narrow channels reach 4 to 6 knots, which is 7.4 to 11.1 km/h. The Gulf Stream runs at 2 to 4 knots, or 3.7 to 7.4 km/h. A sailboat doing 6 knots through the water with a 3-knot adverse current makes only 3 knots over the ground. Skippers time passages to use the tide, and GPS shows speed over ground, which differs from the log reading.
Boat speed and wind speed
Wind speed in a forecast is also in knots. A force 7 near gale is 28 to 33 knots, which is 52 to 61 km/h, and force 10, a storm, is 48 to 55 knots, which is 89 to 102 km/h. The sea state grows with wind speed and fetch. Many sailors know the Beaufort scale by heart, and for guests ashore a “convert knots to km/h” calculation puts the forecast in familiar terms.
Planing dinghies and skiffs
A dinghy planing downwind reaches 12 to 20 knots, which is 22 to 37 km/h. High-performance skiffs hit 25 to 30 knots, which is 46 to 56 km/h. A rowing eight does 11 to 12 knots, or 20 to 22 km/h, in a race. The comparison is surprising to people who think sailing boats are slow.
Motorboats
A typical fishing boat cruises at 8 to 10 knots, which is 15 to 18.5 km/h. A sport cruiser at 25 knots does 46 km/h. Offshore powerboat racers reach 100 knots, which is 185 km/h. Fuel use rises with the cube of speed near hull speed, so a motorboat running at planing speed burns much more per mile than a displacement cruiser at 7 knots.
More values for convert knots to km/h
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 kn = 0.1852 km/h
- 0.5 kn = 0.926 km/h
- 3 kn = 5.556 km/h
- 4 kn = 7.408 km/h
- 7 kn = 12.964 km/h
- 15 kn = 27.78 km/h
- 20 kn = 37.04 km/h
- 75 kn = 138.9 km/h
- 200 kn = 370.4 km/h
- 500 kn = 926 km/h
- 2,000 kn = 3,704 km/h
- 10,000 kn = 18,520 km/h
Common slips when you convert knots to km/h
Using 1.609
1.609 converts miles to kilometres. A nautical mile is 1.852 km, so a knot is more than a mile per hour.
Dividing instead of multiplying
From knots to km/h the number grows. If 20 knots became 10.8, you divided.
Saying knots per hour
A knot is already a speed. "Knots per hour" would be an acceleration, which is not what is meant.
Short answers
How do I convert knots to km/h?
Multiply by 1.852.
What is 10 knots in km/h?
18.5 km/h.
What is 20 knots in km/h?
37 km/h.
How many knots is 1 km/h?
0.54 knots.
Does my number leave my device?
No, the calculation runs in your browser.
More pages and a wrap-up
For other speed conversions see Convert knots to m/s, Convert knots to mph, Convert mph to km/h, Convert ft/s to km/h, Convert km/h to Mach, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. The reverse direction is Convert km/h to knots.
In short, a “convert knots to km/h” calculation means multiplying by 1.852 and writing the unit beside the answer. Your number is computed locally, with no account and no upload.