Convert knots to m/s knots ↔ metres per second Free Online Secure
Type a value in knots and read it in metres per second 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 metres per second
Common values — Convert knots to m/s (knots ↔ metres per second)
| kn | m/s |
|---|---|
| 1 | 0.514444444444 |
| 2 | 1.02888888889 |
| 3 | 1.54333333333 |
| 5 | 2.57222222222 |
| 10 | 5.14444444444 |
| 20 | 10.2888888889 |
| 50 | 25.7222222222 |
| 100 | 51.4444444444 |
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 data in knots, physics in metres per second
Marine forecasts, ship logs and racing results speak in knots. Buoy networks, scientific papers and every physics equation speak in metres per second. Anyone who works with both, whether an oceanography student, a naval architect or a sailor who wants to know how hard the wind is pushing on the rig, needs a dependable way to go from one to the other. To convert knots to m/s, multiply by 0.5144: 10 knots is 5.14 m/s, 30 knots is 15.43 m/s and 100 knots is 51.44 m/s. The calculator above does the multiplication as you type, and the sections below explain what the figures mean at sea and in the lab.
You will find the rule with worked examples, a short profile of each unit, a comparison and a long run of real situations where the switch matters, followed by common slips. The arithmetic runs in your browser and your numbers are not sent anywhere. For navigation decisions, rely on official forecasts and on your own judgement.
How to convert knots to m/s: multiply by 0.5144
The rule
A knot is one nautical mile per hour. A nautical mile is 1,852 metres and an hour has 3,600 seconds, so one knot is 1,852 / 3,600 = 0.514444 m/s. To convert knots to m/s, multiply the number of knots by 0.5144. That makes 4 knots 2.06 m/s, 25 knots 12.86 m/s and 450 knots 231.5 m/s. To go back, multiply m/s by 1.9438.
Worked examples
A 22-knot wind is 11.32 m/s. A 14-knot tanker moves at 7.2 m/s. A fast ferry at 35 knots covers 18 metres every second, and a hurricane-force wind of 64 knots is 32.9 m/s.
Why the factor never changes
The nautical mile is defined as exactly 1,852 metres, so the factor is a consequence of two definitions rather than a measured constant. There is no rounding hidden in it.
A quick sanity test
The answer in m/s is a little over half the number of knots. If a “convert knots to m/s” calculation gave a bigger number than you started with, you used the factor for the other direction.
The knot
The seafarer's unit
The knot is the standard speed unit for ships, boats and aircraft, and the usual one for marine and aviation weather. It takes its name from the chip log, a board on a line with knots tied at regular intervals, which sailors paid out over the stern while a sand glass ran.
Where it appears
Marine forecasts, gale warnings, nautical charts, ship specifications and racing results.
The metre per second
The SI unit of speed
The metre per second is the coherent SI unit of speed, which means that equations for momentum, energy, drag and waves work in it without extra constants. Scientific buoys and research cruises report wind and current this way.
Where it appears
Physics and engineering texts, research datasets, buoy records and turbine data sheets.
Knots against metres per second
One knot is 0.514 m/s, so a speed in m/s is a little more than half the number of knots. A 20-knot breeze is 10.3 m/s and a 40-knot gale is 20.6 m/s. Both units describe the same motion, and only the scale of the number differs, much as a mile and a kilometre do.
The conversion is exact, with no rounding hidden in the factor. The one thing to watch is the direction: from knots to m/s the figure falls.
Where the conversion shows up
Buoy data and marine forecasts
The standard meteorological files from moored buoys give wind in m/s, while the marine forecast issued for the same area quotes knots. A buoy reading of 8.2 m/s is 15.9 knots, 12 m/s is 23.3 knots and 17 m/s is 33 knots, the threshold of a gale. To compare the observation with the forecast, convert one of them first.
Naval architecture
Ship speed is quoted in knots in the contract and in m/s inside the resistance and power calculations. A tanker that must make 14 knots needs its hull analysed at 7.2 m/s. Every table that links speed and power therefore carries both columns.
Safety limits
Crane lifts, drone flights and boat transfers at offshore sites all have wind limits. Manufacturers state them in m/s, while the forecast arrives in knots, so crews convert before they decide.
Wind profile with height
Wind is slower near the sea surface and stronger higher up. Over open water, a common rule of thumb scales the speed by a power law with an exponent near 0.11. A 20-knot wind at 10 metres, which is 10.3 m/s, becomes about 25.8 knots, or 13.3 m/s, at 100 metres, the height of a turbine hub. Forecasts for the surface are quoted in knots, and wind-farm studies in m/s.
Small drones
A small camera drone is usually rated to hold position in wind up to about 10 m/s, which is 19.4 knots. Pilots who operate near the coast hear their wind in knots from the harbour office and in m/s from the aircraft's app. Gusts matter as well: a 12 m/s gust is 23.3 knots, enough to push a light drone off its track.
Airliners and the speed of sound
An airliner cruises at about 450 knots, which is 231.5 m/s. The speed of sound at cruise altitude is near 295 m/s, so the aircraft flies at about Mach 0.78. Air traffic control speaks in knots and the aerodynamicist in m/s and Mach number, and the figure of 231.5 m/s lets the two compare notes.
The mental shortcut
To convert knots to m/s in your head, halve the knots and add 3 per cent. For 20 knots: half is 10, plus 3 per cent is 10.3 m/s. For 50 knots: half is 25, plus 3 per cent is 25.75 m/s. The method is within a fraction of a per cent, which is more than enough when you are reading a forecast on deck.
Spreadsheet formulas
To convert knots to m/s in a spreadsheet, put the knots in column A and type =A2*0.514444 in column B. For the reverse, use =B2*1.943845. Add a column for wind pressure with =0.5*1.225*B2^2 and one for the energy of a moving boat. Give every column a heading with its unit, and keep at least four decimals in the factor so that squared terms stay accurate.
Rounding and precision
When you convert knots to m/s, the factor is exact: 10 knots is 5.1444 m/s. Two decimals are enough to report a result, 5.14 m/s. When the speed is squared or cubed later in a formula, carry the full digits until the very last step, because rounding 5.14 to 5.1 before squaring gives an error of nearly 1 per cent.
Landmarks to memorise
To convert knots to m/s by eye, anchor on these values: 5 knots is 2.6 m/s, 10 knots is 5.1 m/s, 20 knots is 10.3 m/s, 30 knots is 15.4 m/s, 50 knots is 25.7 m/s and 100 knots is 51.4 m/s. With these six anchors, almost any value in a bulletin can be placed by eye.
Checking by reversing
To check any convert knots to m/s result, multiply the answer by 1.9438. If 10 knots became 5.14 m/s, then 5.14 times 1.9438 returns 10. A second test is the size of the result: the figure in m/s should be just above half the figure in knots.
Link to km/h
One knot is 1.852 km/h and one m/s is 3.6 km/h, which is how 0.514 comes about. A 20-knot vessel makes 37 km/h and 10.3 m/s. Rivers and canals often post limits in km/h, open water uses knots, and a physics paper uses m/s, so a sailor may meet all three in a single week.
Kinetic energy of a moving boat
Kinetic energy is half the mass times the speed squared, with speed in m/s. A one-tonne dinghy at 10 knots, 5.14 m/s, carries about 13.2 kJ. A ten-tonne cruiser at 5 knots, 2.57 m/s, carries 33.1 kJ. Doubling the speed quadruples the energy, which is why berthing speed matters so much.
Power in the wind
The power flowing through each square metre of the wind is half the air density times the cube of the speed. At 6 m/s, about 11.7 knots, that is roughly 130 W per square metre. At 10 m/s, 19.4 knots, it is 610 W, and at 12 m/s, 23.3 knots, it is 1,060 W. Because of the cube, a modest rise in knots brings a large rise in available power, which is why turbine designers care so much about the exact m/s figure.
A worked example
A passage of 48 nautical miles at 6 knots takes 8 hours. The same speed is 3.0867 m/s and the distance is 88,896 metres, and 88,896 divided by 3.0867 gives 28,800 seconds, which is again 8 hours. A “convert knots to m/s” calculation and a division give the same time in any unit.
GRIB files and model output
Before you convert knots to m/s on a chart, note that weather models store wind components in m/s because the equations of motion use SI units. Routing programs convert them to knots for display. If you open a raw GRIB or NetCDF file in a script, the numbers you see are in m/s, and a single multiplication by 1.9438 matches them to the knots shown in your chart plotter.
Gusts against the mean
A gust is a short peak, usually averaged over three seconds, and it can exceed the ten-minute mean by 30 to 40 per cent. A mean of 20 knots, 10.3 m/s, can bring gusts near 27 knots, 13.9 m/s. A buoy that records its mean in m/s and a forecast that quotes gusts in knots must be put on the same footing before they are compared.
Pressure on an anchored vessel
Wind force on a moored hull grows with the square of the speed. At 30 knots, 15.4 m/s, it is 2.25 times what it is at 20 knots, 10.3 m/s. Anchor manufacturers publish holding data against wind in m/s, and the forecast is in knots, so the conversion decides whether the scope of chain you laid is enough.
Tidal stream turbines
Underwater turbines in tidal channels start generating at a stream of about 1 m/s, which is 1.9 knots, and reach rated output near 3 m/s, 5.8 knots. The power available grows with the cube of the speed, so a spring tide that is only a knot stronger can double the output. Developers publish stream speeds in m/s, while the skippers of the service boats read the same stream in knots.
Kite and windsurf sessions
Kitesurfers usually find good conditions from 15 to 25 knots, 7.7 to 12.9 m/s, and windsurfers start planing near 12 knots, 6.2 m/s. Beach anemometers and club websites often show m/s, while the sail manufacturer's chart recommends sizes by knots. A quick table of both units keeps the right kit in the bag.
Paddlers and small craft
A touring kayak moves at about 3 knots, 1.5 m/s, and a trained racing paddler at 5 knots, 2.6 m/s. A stand-up paddleboard manages around 2 knots, 1 m/s. If you log paddling pace in m/s from a sports watch, a “convert knots to m/s” calculation lets you compare it with the speeds on a tidal-stream chart.
Weather radar
Doppler radar measures radial velocity in m/s. A storm cell approaching at 15 m/s is moving at about 29 knots. Forecast offices that warn mariners turn the radar values into knots so that skippers can use them straight away to estimate arrival time.
Lifeboats and rescue craft
An all-weather lifeboat typically makes about 25 knots, 12.9 m/s, and a small inshore rescue boat around 30 knots, 15.4 m/s. At 25 knots, ten nautical miles take 24 minutes. Rescue coordinators think in knots and nautical miles, while the people who test the boats' hulls and engines record trial runs in m/s, so a table with both columns saves time when reports are compared.
Warning thresholds
A gale warning begins at 34 knots, 17.5 m/s. Storm force begins at 48 knots, 24.7 m/s, and hurricane force at 64 knots, 32.9 m/s. Small craft advisories often start near 25 knots, 12.9 m/s. Knowing the thresholds in both units prevents confusion when a scientific report and a bulletin describe the same event.
Tsunami speed
A tsunami in the open ocean moves at the square root of gravity times depth. Over 4,000 metres of water that is 198 m/s, which is 385 knots, close to the cruise speed of a small jet. Over 200 metres of depth it slows to 44 m/s, or 86 knots, and in 50 metres to 22 m/s, or 43 knots. The wave is slow to build up in the open sea and fast to arrive.
Whales and dolphins
A bottlenose dolphin can reach bursts of around 20 knots, 10.3 m/s, and a hunting orca is often quoted at about 30 knots, 15.4 m/s. A blue whale cruises much more slowly, near 5 knots, 2.6 m/s. Wildlife researchers log tracks in m/s, while skippers sharing the water with them compare those speeds with their own log in knots.
Reading wind arrows on a chart
Meteorological charts show wind with barbs, each full feather meaning 10 knots, 5.1 m/s, and each half feather 5 knots, 2.6 m/s. A symbol with two full feathers and one half feather therefore stands for 25 knots, 12.9 m/s. Researchers who plot barbs from data in m/s must convert knots to m/s first or the symbols will mislead.
A fast ferry crossing
A fast ferry crossing 60 nautical miles at 35 knots takes about 103 minutes. At 35 knots the vessel moves at 18 m/s, so it covers its own length of 90 metres in five seconds. A passenger watching the speed display in knots and a marine surveyor reading the log in m/s are describing exactly the same crossing.
The Froude number
Naval architects judge how a hull makes waves with the Froude number, speed divided by the square root of gravity times length. For a 300-metre container ship at 22 knots, 11.3 m/s, the figure is 0.21. For a 250-metre tanker at 14 knots, 7.2 m/s, it is 0.15. The formula demands m/s, but the owner asks about knots, and the designer has to switch between the two many times a day.
Aircraft carrier operations
A carrier turns into the wind so that the air flowing over the deck helps aircraft take off and land. Wind over deck of 25 to 30 knots, about 13 to 15 m/s, is a typical target. A steam catapult launches a fighter to around 150 knots, 77 m/s, within a track about 100 metres long. Crews work in knots, and the engineers who size the catapult work in m/s.
Foiling racing boats
Modern foiling yachts rise out of the water and sail at three or four times the speed of the wind in some conditions. A boat at 45 knots is making 23 m/s, and one at 50 knots makes 25.7 m/s. The speed record under sail stands at 65.45 knots, 33.7 m/s. Race organisers publish speeds in knots, while the tank-testing data behind the designs is in m/s.
Sailing polars
A polar diagram shows the speed a boat can reach at every angle to the wind for a given wind speed. Software often takes the wind in knots and gives the boat speed in knots, but research versions work in m/s. When you import a polar into a model that uses SI units, convert every row once, and write the unit in the heading of the column so that nobody has to guess.
Search and rescue drift
A person in the water, or a liferaft without a canopy, drifts downwind at roughly a few per cent of the wind speed. In a 20-knot wind, 10.3 m/s, a rough figure of 3 per cent gives 0.6 knots, or 0.3 m/s, about 1,100 metres each hour. Rescue planners use leeway tables that give the rate as a fraction, so the unit of the wind has to match the unit of the drift.
Offshore installation windows
Lifting a turbine blade from a vessel is allowed only below a certain mean wind, often around 10 m/s, which is 19.4 knots, depending on the crane and the load. A project manager reading a forecast of 22 knots, 11.3 m/s, therefore sees at once that the limit is exceeded. The weather window is a conversion exercise as much as a planning one.
More values for convert knots to m/s
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 = 0.0514444 m/s
- 0.5 kn = 0.257222 m/s
- 3 kn = 1.54333 m/s
- 4 kn = 2.05778 m/s
- 7 kn = 3.60111 m/s
- 15 kn = 7.71667 m/s
- 20 kn = 10.2889 m/s
- 75 kn = 38.5833 m/s
- 200 kn = 102.889 m/s
- 500 kn = 257.222 m/s
- 2,000 kn = 1,028.89 m/s
- 10,000 kn = 5,144.44 m/s
Common slips when you convert knots to m/s
Multiplying by 1.9438
From knots to m/s the number falls. If 10 knots turned into 19, you used the factor for the opposite direction.
Treating a knot as a kilometre per hour
A knot is 1.852 km/h, not 1 km/h. Mixing the two gives an error of 85 per cent.
Rounding too early
If the speed is squared later in a formula, rounding first magnifies the error. Keep full digits until the end.
Short answers
How do I convert knots to m/s?
Multiply the knots by 0.5144.
How many m/s is 10 knots?
5.14 m/s.
How many m/s is 30 knots?
15.43 m/s.
How many knots is 1 m/s?
1.944 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 mph, Convert knots to km/h, Convert c to m/s, Convert km/h to m/s, Convert m/s to mph, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. The reverse direction is Convert m/s to knots.
In short, a “convert knots to m/s” calculation comes down to multiplying by 0.5144 and writing the unit beside the answer. Your number is computed locally, with no account and no upload.