Convert m/s to knots metres per second ↔ knots Free Online Secure
Type a value in metres per second 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 metres per second
Common values — Convert m/s to knots (metres per second ↔ knots)
| m/s | kn |
|---|---|
| 1 | 1.94384449244 |
| 2 | 3.88768898488 |
| 3 | 5.83153347732 |
| 5 | 9.7192224622 |
| 10 | 19.4384449244 |
| 20 | 38.8768898488 |
| 50 | 97.192224622 |
| 100 | 194.384449244 |
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.
From the laboratory to the helm: scientific wind data in knots
Research papers, model output, wind-tunnel reports and engineering data sheets are written in metres per second. Chart tables, radio calls and the instruments of a boat or an aircraft speak in knots. The step between them is small, but it has to be right, because the person reading a record of 20 m/s may be about to decide whether to leave harbour. To convert m/s to knots, multiply by 1.9438: 5 m/s is 9.72 knots, 10 m/s is 19.44 knots and 20 m/s is 38.88 knots. The calculator above multiplies as you type, and the sections below show what the numbers mean for seafarers, pilots and anyone who has to carry data from a scientific source to a practical one.
You will find the rule with worked examples, a short profile of each unit, a comparison and a long series of practical settings, then the common slips. The calculation runs in your browser and your figures are not sent anywhere. For safety decisions rely on official forecasts and on your own judgement.
How to convert m/s to knots: multiply by 1.9438
The rule
One metre per second covers 3,600 metres in an hour. A nautical mile is 1,852 metres, so 3,600 divided by 1,852 gives 1.943844. To convert m/s to knots, multiply the m/s figure by 1.9438. That makes 3 m/s equal to 5.83 knots, 12 m/s equal to 23.33 knots and 40 m/s equal to 77.75 knots. To go in the other direction, multiply knots by 0.5144.
Worked examples
A breeze of 4 m/s is 7.8 knots. A wind of 15 m/s is 29.2 knots. A storm of 25 m/s is 48.6 knots, and a gust of 33 m/s passes the hurricane threshold of 64 knots.
Why the factor is exact
The nautical mile is defined as exactly 1,852 metres and an hour as exactly 3,600 seconds, so the factor follows from definitions and not from a rounded measurement. It is identical in every country.
A quick sanity test
The answer in knots is nearly double the figure in m/s. If a “convert m/s to knots” calculation gave you a smaller number than the one you began with, the factor was applied the wrong way round.
The metre per second
The unit of scientific data
The metre per second is the SI unit of speed. Reanalysis datasets, forecast models and field instruments from research stations give wind and current in it, because the equations of fluid motion are written in SI units and need no extra constants.
Where it appears
Textbooks, research papers, model files, turbine data sheets and wind-tunnel reports.
The knot
The unit of the helm
The knot is one nautical mile per hour and the working unit of navigation by sea and air. Its name goes back to the chip log, a line knotted at regular intervals and paid out from the stern to find a ship's speed.
Where it appears
Marine forecasts, nautical charts, ship logs, radio calls and aviation weather.
Metres per second against knots
One m/s is 1.944 knots, so the figure in knots is nearly double. A breeze of 6 m/s is 11.7 knots and a wind of 20 m/s is 38.9 knots. A report of 10 m/s must never be read as 10 knots: the real wind is almost 94 per cent stronger than that.
The conversion is exact, and no rounding hides in the factor. The one trap is the direction: from m/s to knots the number grows.
Where the conversion shows up
The Beaufort table in m/s
The standard Beaufort table lists limits in m/s: force 6 is 10.8 to 13.8 m/s, which is 21 to 27 knots. Force 8 is 17.2 to 20.7 m/s, or 33 to 40 knots, and force 10 is 24.5 to 28.4 m/s, or 48 to 55 knots. A sailor reading the table in m/s has to translate it to the knots on the bulletin.
Model output and research data
Global forecast models, such as the ones run in Europe, deliver wind in m/s. Charts made for mariners from the same data show knots. If you download raw fields to plan a passage, the first job is a “convert m/s to knots” calculation.
Equipment specifications
Turbine, mast and drone data sheets state wind limits in m/s. The crew who must decide on the day work from a forecast in knots, so the limit has to be converted before the decision.
The ECMWF and other global models
Global weather models store wind as two components, east-west and north-south, each in m/s. A pair of 7.0 and 5.0 m/s combines to 8.6 m/s, or 16.7 knots. Routing software performs the vector sum and then the conversion. Because the factor is linear, you can convert m/s to knots on each component or on the combined speed and get the same result, but you must still do the vector sum.
Mental conversion
To convert m/s to knots in your head, double the m/s figure and take away 3 per cent. For 15 m/s: 30 minus 0.9 gives 29.1 knots. For 40 m/s: 80 minus 2.4 gives 77.6 knots. The error is under a tenth of a knot.
Spreadsheets
Put the m/s values in column A and enter =A2*1.943844 in column B. For the opposite direction use =B2*0.514444. Add a column that looks up the Beaufort force with a table of lower limits, so each row shows the speed in both units and the sea state it implies.
Rounding for safety
8 m/s is 15.55 knots, which you can write as 15.6 or 16. When the figure is compared with a safety limit, round up, towards the stronger wind, so that you err on the safe side. Rounding down could leave a small boat on the water on a day when the gusts are too strong.
Landmarks to memorise
1 m/s is nearly 2 knots. 5 m/s is 9.7 knots, 10 m/s is 19.4 knots, 15 m/s is 29.2 knots, 20 m/s is 38.9 knots and 30 m/s is 58.3 knots. To convert m/s to knots on the fly, remember these six values and interpolate between them.
Reference ladder
0.5 m/s is 0.97 knots. 2 m/s is 3.89 knots. 7.7 m/s is 14.97 knots. 13.8 m/s is 26.83 knots. 17.2 m/s is 33.43 knots. 24.5 m/s is 47.62 knots. 32.7 m/s is 63.56 knots. These landmarks are the upper limits of Beaufort forces.
Checking by reversing
To check a “convert m/s to knots” calculation result, multiply the answer by 0.5144. If 10 m/s turned into 19.44 knots, 19.44 times 0.5144 returns 10. A second test concerns size: the knots figure must be a little under double the m/s figure.
Relation to km/h
One m/s is 3.6 km/h and one knot is 1.852 km/h. That makes 10 m/s equal to 36 km/h, or 19.4 knots. Divide a km/h figure by 1.852 to get knots, or pass through m/s first. All three express the same motion on different scales.
Dynamic pressure and sail loads
Dynamic pressure at 8 m/s is 39 Pa, at 15 m/s 138 Pa and at 25 m/s 383 Pa. In knots the speeds are 15.6, 29.2 and 48.6. A sailmaker who gives reefing advice in knots and a designer who calculates loads in m/s are talking about the same thing, and the conversion lets them compare notes.
A worked example
A vessel starts a passage of 90 nautical miles at 5 m/s. That speed is 9.72 knots, so the passage takes 9.26 hours. In metres the distance is 166,680, and dividing by 5 gives 33,336 seconds, again 9.26 hours. Any unit gives the same answer when you convert m/s to knots and divide.
Coastal stations and offshore wind
A coastal anemometer at 10 metres above land may read 6 m/s, 11.7 knots, while the wind a few miles offshore at the same time is 9 m/s, 17.5 knots. A sailor who trusts only the shore station underestimates conditions at sea. Official marine forecasts account for the difference, and raw station data do not.
Wind-tunnel results
A test of a sail or a hull appendage in a wind tunnel is run at 10, 15 or 20 m/s, depending on the facility. To convert m/s to knots for these runs, apply the factor to each speed: they correspond to 19.4, 29.2 and 38.9 knots. The designer who wants to know how the sail behaves in a force 7 on the water reads the report in m/s, then the forecast in knots, and links them through the factor 1.9438.
Mean and gust
Automatic stations log the mean wind and the maximum gust, both in m/s. A mean of 7 m/s, 13.6 knots, with gusts to 11 m/s, 21.4 knots, shows a large spread and a risk of knockdowns for light boats. The ratio between gust and mean is a useful indicator of how unsettled the air is.
Oars and outboards
An elite rower in a racing boat reaches about 5 m/s, 9.7 knots. A rigid inflatable with a 15-horsepower outboard may exceed 7 m/s, 13.6 knots. If you record sessions on a sports watch that shows m/s, a “convert m/s to knots” calculation tells you how the effort compares with the numbers on a marina's speed signs.
Harbour pilots and wind reports
Pilots get wind reports from the port control in knots or m/s, according to local rules. A pilot who hears 12 m/s must know it means 23 knots, enough to stop a small tug from working. The number is passed over the radio, so the unit should be spoken clearly to avoid mistakes.
Wave speed from the period
A swell with a period of 12 seconds travels at nearly 18.7 m/s, which is 36 knots. The wave is faster than any ordinary ship, which is why swell reaches a shore well before the storm that created it. Wave charts give the period in seconds and the phase speed in m/s.
Canal and lock operations
On canals and at locks, vessel speed is limited and wind displays may show m/s. A wind of 14 m/s, 27 knots, can postpone the entry of an empty barge into a lock because the high freeboard catches the wind. Operators who handle foreign vessels keep a card with both units.
Airliners and Mach number
An airliner at 230 m/s is flying at 447 knots, roughly two thirds of the speed of sound at sea level. Pilots use knots and Mach number, while engineers work in m/s. At cruise altitude the sound speed is lower, around 295 m/s, so the same aircraft is near Mach 0.78.
Helicopters and offshore platforms
Helicopter operations to an offshore platform are limited by wind, and some procedures set an upper limit near 60 knots, which is 31 m/s. A technical manual in SI units gives 31 m/s, while the crew works in knots. A “convert m/s to knots” calculation puts the two documents on the same footing before the flight.
Wind and wave height
A wind of 10 m/s, 19.4 knots, blowing over a wide fetch raises waves of around 1.5 to 2 metres. At 15 m/s, 29.2 knots, they grow toward 3 to 4 metres, and at 20 m/s, 38.9 knots, they exceed 5 metres. The figures are indicative, but they show why a bulletin in m/s and one in knots must tell the same story.
How an anemometer works
A cup anemometer spins at a rate proportional to wind speed, and the electronics turn the rotation into m/s. A display reading 9.5 m/s on a pier means 18.5 knots, force 5, the point at which many small boats stay ashore. The conversion is made by whoever reads the display, since few anemometers show both units.
Club racing rules
A sailing club may stop youth training when the wind exceeds 8 m/s, which is 15.6 knots. For larger dinghies the limit might be 12 m/s, 23 knots. Writing the rule in both units on the notice board removes the arguments on the pontoon.
Research vessels
Research cruises log wind from the ship's sensors in m/s so that the data fit the scientific archive. The captain, however, runs the ship in knots. A recorded wind of 14 m/s is 27.2 knots, enough to stop a deployment of delicate instruments over the side. The same figure carries two meanings in two cabins.
Inland lakes and boats
Powerboat limits on lakes are posted in km/h or knots, while hydrological stations report the current in m/s. Combining them in a trip plan means choosing one unit and sticking to it. Knots is the natural choice if distances are in nautical miles and m/s if you work in metres.
Weather map colours
Synoptic maps shade areas by wind speed bands in m/s, for instance 10 to 15 in yellow and 15 to 20 in orange. In knots, yellow covers 19 to 29 and orange 29 to 39. Writing the knots equivalents in the margin of a chart takes a minute and prevents misreadings at sea.
Wind turbine data sheets
A typical turbine starts producing at 3 m/s, reaches rated power near 12 m/s and shuts down at 25 m/s. In knots those are 5.8, 23.3 and 48.6. A technician climbing a turbine from a boat checks the forecast in knots against the manufacturer's access limit, often given as a mean wind in m/s.
Sprinters and animals
The top speed of a world-class sprinter is about 12.4 m/s, which is 24.1 knots. A cheetah reaches around 29 m/s, or 56 knots. A cyclist at 6 m/s makes 11.7 knots, faster than most cruising yachts. Comparing living things with ships in knots turns abstract speeds into pictures.
Falling from the sky
A skydiver in a belly-to-earth position reaches about 55 m/s, which is 107 knots. A peregrine falcon in a dive has been recorded above 90 m/s, or 175 knots. A strong hurricane has winds of 70 m/s or more, 136 knots, which is still slower than the falcon in a stoop.
Sound and bullets
Sound travels at about 340 m/s, 661 knots. A rifle bullet leaves the barrel at around 800 m/s, 1,555 knots, well above the speed of sound. The knot is built for ships and aircraft, so figures like these look unusually large when you convert them, and that is the signal that you have moved outside its natural range.
Orbital velocities
The International Space Station circles Earth at 7,660 m/s, which is 14,890 knots. A passenger jet at 230 m/s, 447 knots, is thirty-three times slower. Astronomers and flight engineers do not use knots for orbits, but the conversion shows the contrast in a way that people used to maritime speeds can grasp.
Rivers and estuaries
Hydrologists record river flow in m/s. A current of 1.5 m/s is 2.9 knots, typical for a large river in flood. A motor launch that makes 3 knots in still water would barely move upstream. In estuaries the tide adds to the river, so the sailor needs to read the gauge in knots to compare it with the boat's speed.
More values for convert m/s 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 m/s = 0.194384 kn
- 0.5 m/s = 0.971922 kn
- 3 m/s = 5.83153 kn
- 4 m/s = 7.77538 kn
- 7 m/s = 13.6069 kn
- 15 m/s = 29.1577 kn
- 20 m/s = 38.8769 kn
- 75 m/s = 145.788 kn
- 200 m/s = 388.769 kn
- 500 m/s = 971.922 kn
- 2,000 m/s = 3,887.69 kn
- 10,000 m/s = 19,438.4 kn
Common slips when you convert m/s to knots
Multiplying by 0.5144
From m/s to knots the number grows. If 10 m/s turned into 5, you used the factor for the opposite direction.
Reading m/s as knots
A bulletin of 10 m/s is not 10 knots. The true wind is 19.4 knots, nearly double, and the mistake can turn a pleasant day into a dangerous one.
Rounding down at a limit
When comparing with a safety threshold, round towards the larger number, not the smaller.
Short answers
How do I convert m/s to knots?
Multiply the m/s figure by 1.9438.
How many knots is 10 m/s?
19.44 knots.
How many knots is 20 m/s?
38.88 knots.
How many m/s is 1 knot?
0.514 m/s.
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 m/s to km/h, Convert m/s to ft/s, Convert mph to knots, Convert km/h to knots, Convert knots to mph, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. The reverse direction is Convert knots to m/s.
In short, a “convert m/s to knots” calculation comes down to multiplying by 1.9438 and writing the unit beside the answer. Your number is computed locally, with no account and no upload.