Convert km/h to knots kilometres per hour ↔ knots Free Online Secure
Type a value in kilometres per hour and read it in knots at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Convert from kilometres per hour
Common values — Convert km/h to knots (kilometres per hour ↔ knots)
| km/h | kn |
|---|---|
| 1 | 0.539956803456 |
| 2 | 1.07991360691 |
| 3 | 1.61987041037 |
| 5 | 2.69978401728 |
| 10 | 5.39956803456 |
| 20 | 10.7991360691 |
| 50 | 26.9978401728 |
| 100 | 53.9956803456 |
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.
River cruises, canal passages and cargo ships: from km/h to knots
A brochure for a Danube river cruise gives the ship's pace as roughly 20 kilometres per hour, while the captain, the pilot and the port authority count in knots. Canal rules may post a limit in km/h on one waterway and in knots on the next. Anyone who follows a vessel from river to sea meets both units. To convert km/h to knots, multiply by 0.54: 20 km/h is 10.8 knots, 37 km/h is 20 knots and 100 km/h is 54 knots. The calculator above multiplies as you type, and the sections below show what these numbers mean for river and canal traffic, cargo timetables and ferries.
Expect the rule with worked examples, a profile of each unit, a comparison, a long tour of shipping practice and the slips to avoid. All arithmetic stays in your browser, and you should always rely on official documents for navigation.
How to convert km/h to knots: multiply by 0.54
The rule
One knot is exactly 1.852 km/h, so one km/h is 0.539957 knots. To convert km/h to knots, multiply the km/h figure by 0.54. So 15 km/h is 8.1 knots, 40 km/h is 21.6 knots and 60 km/h is 32.4 knots. To go back, multiply the knots by 1.852.
Worked examples
A river cruise ship at 22 km/h makes 11.9 knots. A container ship at 40 km/h makes 21.6 knots. A fast ferry at 65 km/h makes 35.1 knots, and a patrol boat at 90 km/h makes 48.6 knots.
Why 0.54
A nautical mile is 1,852 metres, so to turn kilometres per hour into nautical miles per hour you divide by 1.852, which is the same as multiplying by 0.54. A handy estimate is to halve the figure and add 4 per cent.
A quick sanity test
The knots figure is always 46 per cent smaller than the km/h figure. If a “convert km/h to knots” calculation result is bigger, you used 1.852 instead of 0.54.
The kilometre per hour
The unit of rivers and roads
The kilometre per hour is how brochures, river authorities and tourists describe speed. Inland waterways in Europe often post limits in km/h, as do canal authorities, because the traffic shares signs and rules with road users.
Where it appears
River cruise brochures, canal speed limits and tourist information.
The knot
The unit of the sea
The knot is a nautical mile per hour. Sea-going ships, charts, pilots and port authorities use it, and it carries over to the large rivers that ships enter. A captain moving from a river into a canal and then the sea sees the unit change from km/h to knots on the signs.
Where it appears
Ship logs, pilot instructions, charts and canal transit rules.
Side by side
A knot is 1.852 km/h, so a speed in knots is the smaller number. A river cruise at 22 km/h is under 12 knots, a gentle pace for a ship, while a container ship at 40 km/h makes 21.6 knots, which is brisk at sea. The km/h figure looks larger but says the same thing.
The factor is exact and adds no rounding. The only trap is direction: from km/h to knots the figure falls.
Where the conversion shows up
River cruising
River cruise ships on the Rhine, Danube and Rhône cruise at 18 to 25 km/h, which is 9.7 to 13.5 knots, in still water. The current changes the speed over the ground: on the Danube downstream a ship may make 25 km/h, which is 13.5 knots, while going up against the stream it makes 15 km/h, which is 8.1 knots. A “convert km/h to knots” calculation helps work out the schedule from the log.
Canal transits
The Suez Canal limits ships to about 8 knots, which is 14.8 km/h, in the narrow stretch, so the 193-kilometre passage takes 11 to 16 hours depending on convoys and waiting. Smaller canals have limits of 6 to 10 km/h, which is 3.2 to 5.4 knots, to protect banks from wash. Signs on a European canal might be in km/h, and the pilot's instructions in knots.
Cargo ships
Container ships cruise at 37 to 44 km/h, which is 20 to 24 knots, and bulk carriers and tankers at 24 to 30 km/h, which is 13 to 16 knots. A voyage of 5,000 nautical miles, which is 9,260 km, takes 10.4 days at 20 knots and 14.9 days at 14. The timetable and the fuel bill follow from the speed.
Slow steaming
Fuel use rises roughly with the cube of speed. Cutting a container ship from 24 knots, which is 44.4 km/h, to 18 knots, which is 33.3 km/h, reduces power by about 58 per cent, and fuel per nautical mile by about 44 per cent, at the cost of a longer voyage. This slow steaming became common when fuel prices rose, and shipping lines now describe their schedules in knots and days.
Currents and speed over ground
A ship's log reads speed through water, while GPS reads speed over ground. A river with a 6 km/h current, which is 3.2 knots, adds or subtracts this from the ship's own speed. A cruise ship at 20 km/h, or 10.8 knots, through the water makes 26 km/h, or 14 knots, downstream and 14 km/h, or 7.6 knots, upstream.
Time and distance on a chart
Charts show distance in nautical miles and use the latitude scale. A passage of 120 nautical miles, which is 222 km, at 12 knots, which is 22.2 km/h, takes 10 hours. The same distance in km at 22.2 km/h also takes 10 hours. The rule is to keep units consistent: knots with nautical miles, km/h with km.
Spreadsheet formulas
Place speeds in km/h in column A and use =A2*0.539957 in column B. For the reverse, use =B2*1.852. Add a column for time, =distance_in_nm/B2. Label each column with its unit and use one decimal for knots.
Rounding and precision
The factor is exact: 22 km/h is 11.879 knots. A ship's log reads to a tenth of a knot, so 11.9 is enough. A brochure that says "about 12 knots" is just as informative. Round to the precision of the source, and avoid decimals that suggest false precision.
Doing it in your head
Take half of the km/h figure and add four per cent of the half. For 50 km/h, half is 25 and four per cent of it is 1, giving 26 against an exact 27. For a closer result add eight per cent: 100 km/h gives 50 plus 4, which is 54 knots, exactly right.
Landmarks to memorise
10 km/h is 5.4 knots, 20 km/h is 10.8 knots, 37 km/h is 20 knots, 56 km/h is 30 knots, 93 km/h is 50 knots and 185 km/h is 100 knots. These landmarks help you read a nautical document without a calculator.
Reference ladder
5 km/h is 2.7 knots. 15 km/h is 8.1 knots. 25 km/h is 13.5 knots. 40 km/h is 21.6 knots. 60 km/h is 32.4 knots. 80 km/h is 43.2 knots. 120 km/h is 64.8 knots. 150 km/h is 81 knots. A ladder like this makes a quick check easy.
Checking by reversing
To check any convert km/h to knots result, multiply it by 1.852. If 40 km/h became 21.6 knots, then 21.6 times 1.852 is 40. A second test is the size: the knots figure should be a little more than half the km/h figure.
Relation to mph and m/s
One knot is 1.151 mph and 0.514 m/s. A ship at 20 knots does 23 mph and 10.3 m/s. American river and lake boaters often use mph, and the same boat on the sea uses knots. A table with all four units is a good reference for anyone who works on both.
Why a nautical mile
The nautical mile equals one minute of latitude, so distance on a chart can be measured against the latitude scale on its edge. A knot, one nautical mile per hour, then equals one minute of latitude per hour. Ships sailing due north at 10 knots change latitude by one degree every six hours. This is why the unit survives despite the metric system.
Fast ferries
A fast ferry across the English Channel makes 35 knots, which is 65 km/h, and covers the 21 nautical miles, or 39 km, in about 35 minutes. A conventional ferry at 20 knots, or 37 km/h, takes 63 minutes plus port time. The speed in km/h appears in the brochure, and the speed in knots on the bridge.
Weather on the river
High water and headwinds slow river traffic. A ship making 20 km/h, which is 10.8 knots, in calm weather may fall to 15 km/h, or 8.1 knots, into a 40 km/h headwind. Inland navigation authorities post water levels and speed limits for narrow reaches. A “convert km/h to knots” calculation on the posted limit tells a pilot whether the instruments need adjustment.
Speed trials
New ships undergo speed trials over a measured course. A ship with a contract speed of 22 knots, which is 40.7 km/h, is tested at full power in good weather. Runs in both directions cancel out the effect of the current. The trial report lists the speed in knots, and the contract conversion for non-specialist readers lists km/h.
Putting it together
A river cruise from Passau to Budapest covers about 600 km at an average of 20 km/h, which is 10.8 knots, taking 30 hours of sailing spread over several days. A “convert km/h to knots” calculation for the average and a division for the time give the same result as the brochure's schedule. The ship's captain keeps the same figures in knots in the log.
Houseboats and holiday hire
Holiday boats on rivers and canals are limited to low speeds, often 8 to 10 km/h, which is 4.3 to 5.4 knots. A week-long hire covers 150 to 250 kilometres, or 81 to 135 nautical miles, including locks. Hire companies state limits in km/h or mph, while the boat's instruments, if any, show knots, so a “convert km/h to knots” calculation helps a first-time skipper plan stops.
Racing on rivers and lakes
Powerboat races on lakes reach 100 to 200 km/h, which is 54 to 108 knots, and rowing crews on a river 20 km/h, which is 10.8 knots. Organisers publish results in km/h for the audience and the nautical bodies record knots. The conversion matters when a record is claimed, since the governing body specifies the unit in which it must be proven.
Ocean liners and cruise ships
A cruise ship cruises at 18 to 22 knots, which is 33 to 41 km/h. In 24 hours it covers 430 to 530 nautical miles, which is 800 to 980 km. Itineraries are drawn so that the ship arrives at the next port at breakfast time. Passengers see the speed on a cabin screen, often with a switch between knots and km/h.
Tugs and pushboats
A pushboat moving six loaded barges on the Mississippi makes about 5 knots upstream, which is 9.3 km/h, and 8 to 10 knots downstream, which is 15 to 19 km/h. Towing speeds on the Rhine and Danube are similar. A pilot plans for the current, and traffic managers use km/h for river kilometre markers and knots in radio calls.
Locks and waiting times
A lock passage takes 20 to 40 minutes, and the approach is made at 4 to 6 km/h, which is 2.2 to 3.2 knots. A canal with 30 locks adds about 15 hours to a journey. When planning a cruise, add the lock time to the transit time, which is the distance divided by the speed. A “convert km/h to knots” calculation for each segment makes the totals add up.
Harbour speed limits
Ports limit speed to 5 to 10 knots, which is 9 to 19 km/h, inside the breakwater. Marinas post 5 knots, or 9.3 km/h, and 3 knots, or 5.6 km/h, near docks. Wash from a fast boat can damage moored vessels. Local authorities sometimes use km/h on signs for the benefit of visitors from the road.
Strait transits
Ships in busy straits keep to traffic separation schemes and limit speed. In the Bosphorus the typical speed is 8 to 10 knots, which is 15 to 19 km/h, with strong currents of up to 5 knots. Pilots are compulsory for large vessels in some straits. The unit on the pilot's card is knots, and the tourist ferry in the same waters advertises its speed in km/h.
Hydrofoils and catamarans
Passenger hydrofoils make 35 knots, which is 65 km/h, and fast catamarans 38 to 42 knots, which is 70 to 78 km/h. They serve lakes and islands, where trips of 100 km take 90 minutes instead of 5 hours on a conventional boat. Timetables show times, and the boat's speed is in knots on its specification sheet.
Rescue and patrol craft
Lifeboats make 20 to 25 knots, which is 37 to 46 km/h, and rigid inflatable rescue craft 35 to 45 knots, which is 65 to 83 km/h. Coast guard cutters make 25 to 30 knots, which is 46 to 56 km/h. A call 20 nautical miles offshore, or 37 km, reaches a 35-knot craft in 34 minutes. A “convert km/h to knots” calculation helps translate such response times for the public.
More values for convert km/h to knots
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 km/h = 0.0539957 kn
- 0.5 km/h = 0.269978 kn
- 3 km/h = 1.61987 kn
- 4 km/h = 2.15983 kn
- 7 km/h = 3.7797 kn
- 15 km/h = 8.09935 kn
- 20 km/h = 10.7991 kn
- 75 km/h = 40.4968 kn
- 200 km/h = 107.991 kn
- 500 km/h = 269.978 kn
- 2,000 km/h = 1,079.91 kn
- 10,000 km/h = 5,399.57 kn
Common slips when you convert km/h to knots
Multiplying by 1.852
From km/h to knots the number falls. If 20 km/h became 37, you used the wrong factor.
Mixing nautical miles and kilometres
A speed in knots and a distance in km give a wrong time. Convert one of them so the units match.
Ignoring the current
A ship's speed through water is not its speed over ground. Say which one you mean before converting.
Quick questions
What is the method for a “convert km/h to knots” calculation?
Multiply the km/h value by 0.54.
What is 20 km/h in knots?
10.8 knots.
What is 100 km/h in knots?
54 knots.
What is 1 knot in km/h?
1.852 km/h.
Is my figure stored or sent?
No, it stays on your device.
Where to go next
Other speed tools are listed here: Convert km/h to m/s, Convert km/h to mph, Convert mph to knots, Convert m/s to knots, Convert knots to m/s, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. For the opposite direction, use Convert knots to km/h.
The takeaway: a “convert km/h to knots” calculation multiplies by 0.54 and labels the result in knots. The figure you enter is processed on your device only.