Convert km/h to mph kilometres per hour ↔ miles per hour Free Online Secure
Type a value in kilometres per hour and read it in miles 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 from kilometres per hour
Convert to miles per hour
Common values — Convert km/h to mph (kilometres per hour ↔ miles per hour)
| km/h | mph |
|---|---|
| 1 | 0.621371192237 |
| 2 | 1.24274238447 |
| 3 | 1.86411357671 |
| 5 | 3.10685596119 |
| 10 | 6.21371192237 |
| 20 | 12.4274238447 |
| 50 | 31.0685596119 |
| 100 | 62.1371192237 |
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.
Car specs and top speeds: from km/h to mph
A European magazine says a new sports car does 0 to 100 km/h in 3.2 seconds and tops out at 320 km/h. An American review of the same car says 0 to 60 mph in 3.1 seconds and a top speed of 199 mph. Same machine, different units. Motoring journalists, car buyers and fans who follow both press worlds need to convert in their heads. To convert km/h to mph, multiply by 0.6214: 100 km/h is 62.1 mph, 250 km/h is 155.3 mph and 320 km/h is 198.8 mph. The calculator above multiplies as you type, and the sections below show how the figures play out for cars, bikes and record machines.
You will find the rule with worked examples, a short profile of each unit, a comparison, a long set of cases from motoring and the slips to avoid. The arithmetic runs in your browser, and what you type is not sent anywhere.
How to convert km/h to mph: multiply by 0.6214
The rule
One mile is exactly 1.609344 kilometres, so one kilometre is 0.621371 miles. To convert km/h to mph, multiply the km/h figure by 0.6214. So 80 km/h is 49.7 mph, 120 km/h is 74.6 mph and 200 km/h is 124.3 mph. To go back, multiply by 1.609.
Worked examples
A city limit of 50 km/h is 31.1 mph. A motorway limit of 130 km/h is 80.8 mph. A limited top speed of 250 km/h is 155.3 mph, and a record of 490 km/h is 304.5 mph.
Why 0.6214
The mile is defined as 1,609.344 metres, so the factor is exact. A handy approximation is that 8 kilometres make 5 miles, so multiply by 5 and divide by 8: 80 km/h is 400 over 8, which is 50 mph.
A quick sanity test
The mph figure is always about 38 per cent smaller than the km/h figure. If a “convert km/h to mph” calculation result is bigger, you multiplied by 1.609 instead.
The kilometre per hour
The unit of most of the world
The kilometre per hour is the road-speed unit in Europe, Asia, Africa, Oceania and most of the Americas. Car makers design their instruments in it first, and specification sheets from most manufacturers quote it.
Where it appears
Specification sheets, European road signs, test reports and race broadcasts.
The mile per hour
The unit of the United States and the United Kingdom
The mile per hour is used on road signs in the United States and the United Kingdom, and in a few other countries. American car magazines, television shows and performance tests quote 0 to 60 mph and top speeds in mph.
Where it appears
American and British road signs, car reviews and speedometers.
Kilometres per hour against miles per hour
One mph equals 1.609 km/h, so a figure in mph is smaller. The classic benchmark 0 to 60 mph is a speed of 96.56 km/h, while the European benchmark is 0 to 100 km/h, which is 62.14 mph. A car takes slightly longer to reach 100 km/h than 60 mph, by about 3.6 per cent on average, so the same car looks a hair slower in European tests.
The factor is exact, so no rounding enters the conversion. The only trap is direction: from km/h to mph the number falls.
Where the conversion shows up
Acceleration benchmarks
A car doing 0 to 60 mph in 4.0 seconds would take about 4.14 seconds to reach 100 km/h if the acceleration were constant. A 3.0-second 0 to 60 car is a 3.1-second 0 to 100 car. Press tests also differ in the rollout rule, which subtracts the first foot of movement in American tests and can shave 0.2 seconds. A “convert km/h to mph” calculation tells you the speed, but the method matters too.
Top speeds
Many European cars are electronically limited to 250 km/h, which is 155 mph, a gentleman's agreement among German makers. Super sports cars reach 320 km/h, or 199 mph, 350 km/h, or 217 mph, and hypercars pass 400 km/h, or 249 mph. A record of 490 km/h is 304.5 mph, the first time a production-based car passed 300 mph.
Land speed records
The outright land speed record stands at 1,228 km/h, which is 763 mph, set by a jet-powered car in 1997 in the Nevada desert, the first to pass the speed of sound on land. Thrust SSC is the reference. A figure in km/h appears in most European accounts, and mph in American ones.
Motorcycles
Racing motorcycles in MotoGP reach about 366 km/h, which is 227 mph, on the longest straights. Production superbikes are electronically limited to 299 km/h, or 186 mph, by a voluntary agreement. Touring bikes cruise at 130 km/h, or 80.8 mph. Rider magazines in the US quote mph, and a “convert km/h to mph” calculation puts the European figures on the same footing.
Aerodynamic drag
Drag force rises with the square of speed, and power with the cube. A car needing 20 kW at 100 km/h, which is 62 mph, needs about 68 kW at 150 km/h, or 93 mph, and 160 kW at 200 km/h, or 124 mph. The jump explains why the last 50 km/h costs so much power, and why record cars carry such large engines.
Tyre speed ratings
Tyres carry speed ratings: H is 210 km/h, which is 130 mph, V is 240 km/h, or 149 mph, W is 270 km/h, or 168 mph, Y is 300 km/h, or 186 mph. A tyre must be rated at or above the car's top speed. The ratings are in km/h, even on American tyres, with mph in the table that follows. A “convert km/h to mph” calculation gives the American equivalents.
Speed cameras and tolerance
In Europe a speed camera might flag 53 km/h in a 50 zone, which is 32.9 mph in a 31 mph zone. In the UK enforcement thresholds are often the limit plus 10 per cent plus 2 mph, so 35 in a 30 zone, which is 56 km/h in a 48 km/h zone. The tolerance depends on the country, and tourists benefit from knowing both the limit and the tolerance.
Spreadsheet formulas
Place speeds in km/h in column A and use =A2*0.621371 in column B. For the reverse, use =B2*1.609344. Add a column with the time for a given distance, =distance_in_miles/B2. Label each column with its unit and use one decimal.
Rounding and precision
The factor is exact: 100 km/h is 62.137 mph. Speedometers show whole numbers, so 62 is enough. For record claims, a speed of 490.48 km/h is 304.77 mph, and sources round differently, which produces slightly different figures in headlines. Quote the original unit if accuracy matters.
A mental shortcut
Multiply by 5 and divide by 8. For 160 km/h: 800 divided by 8 is 100 mph, against an exact 99.4. For 120 km/h: 600 over 8 is 75 mph, against 74.6. The error is 0.6 per cent. Another trick is to take 60 per cent and add one more per cent.
Landmarks to memorise
50 km/h is 31 mph, 80 km/h is 50 mph, 100 km/h is 62 mph, 120 km/h is 75 mph, 130 km/h is 81 mph, 160 km/h is 99 mph and 250 km/h is 155 mph. These landmarks cover most of what a driver meets.
Reference ladder
30 km/h is 18.6 mph. 60 km/h is 37.3 mph. 90 km/h is 55.9 mph. 110 km/h is 68.4 mph. 140 km/h is 87 mph. 180 km/h is 111.8 mph. 200 km/h is 124.3 mph. 300 km/h is 186.4 mph. A ladder like this makes a quick check easy.
Checking by reversing
To check any convert km/h to mph result, multiply it by 1.609. If 100 km/h became 62.1 mph, then 62.1 times 1.609 is 99.9. A second test is the size: the mph number should be about five eighths of the km/h number.
Relation to m/s and knots
100 km/h is 27.78 m/s and 53.99 knots. 62.14 mph is 27.78 m/s too. Physics problems and nautical charts use m/s and knots, and the quick route between them goes through km/h or mph. A table with all four units is useful for people who write about vehicles, boats and aircraft.
Electric cars
Electric cars have strong low-speed acceleration but lower top speeds because of battery and motor limits. A performance electric sedan may claim 322 km/h, or 200 mph, while a typical family electric car is limited to 160 km/h, or 99.4 mph, to protect range. Dashboards offer a switch between km/h and mph, and software updates have occasionally changed the limit.
Stopping distances
The stopping distance at 60 mph, which is 96.6 km/h, is about 73 metres on dry tarmac including reaction time. At 100 km/h, which is 62 mph, it is about 76 metres. The figures vary with tyres and road, but they show that European and American speeds, once converted, give nearly the same distances. The unit matters less than the physics.
The long haul
On a transatlantic road trip, drivers cover distances of 3,000 miles, which is 4,828 km. At an average of 60 mph, which is 96.6 km/h, that takes 50 hours of driving. The same plan in kilometres at 100 km/h takes 48 hours. Rough figures such as these are what people use to plan stops and fuel.
Dashboard dual scales
Dual-scale speedometers print km/h in the larger numbers on European cars and mph in smaller ones, and the reverse on American models. The ratio of 1.6 between the rings gives an easy check: when the needle is at 60 mph, the other scale shows 97 km/h. A “convert km/h to mph” calculation is built into the face of the instrument.
Hybrids and economy cars
An economy hatchback has a top speed of around 180 km/h, which is 112 mph, and cruises happily at 120 km/h, or 75 mph. A hybrid may be limited to 165 km/h, or 103 mph, in electric mode. Reviews list these figures along with fuel economy, and a “convert km/h to mph” calculation puts a European brochure next to an American one, which is useful when comparing models sold in both markets.
Pickup trucks and towing
Towing speed limits are lower than car limits. In Europe a car with a caravan is limited to 80 or 100 km/h, which is 50 or 62 mph, and in many American states to 55 or 65 mph, which is 89 or 105 km/h. A tow vehicle becomes unstable at higher speeds, and manufacturers' guidelines usually say 90 km/h, or 56 mph, at the most.
Buying a used import
A car imported from the United States has a speedometer in mph, and the odometer in miles. A reading of 120,000 miles is 193,121 km. If the speedometer is not converted, the car may be hard to drive in a km/h country. Dashboard clusters can be swapped or reprogrammed, and an inspector will check the results with a GPS device and a “convert km/h to mph” calculation.
Formula One
Formula One cars reach about 350 km/h, or 217 mph, at the end of the longest straights, and the fastest recorded speed in a race is around 372 km/h, which is 231 mph. Cornering speeds of 250 km/h, or 155 mph, are common in fast corners. Commentators switch between units depending on the broadcast language, so a quick conversion helps comparison.
Rally and off-road
Rally cars on gravel reach 180 km/h, or 112 mph, and on tarmac stages 200 km/h, or 124 mph. Off-road trucks in desert races hit 160 km/h, or 99 mph. Speeds are quoted in km/h in European events and mph in American ones, and the same car with the same driver gets different headline numbers.
NASCAR and drag racing
NASCAR cars average over 190 mph on superspeedways, which is more than 306 km/h, with restrictor plates limiting top speed. Drag racing top-fuel dragsters reach 335 mph, or 539 km/h, in 1,000 feet. American audiences are given mph, while international viewers get km/h from graphics, so a “convert km/h to mph” calculation is useful for fans who follow both.
Road signs and speed limits
Typical European limits of 50, 90 and 130 km/h are 31, 56 and 81 mph. British limits of 30, 60 and 70 mph are 48, 97 and 113 km/h. American limits of 25, 55 and 75 mph are 40, 89 and 121 km/h. A driver who moves between regions tracks differences of 5 to 10 km/h only by understanding the pattern, not by memorising every sign.
Speedometer error
Speedometers are required by many regulations to read slightly high, never low. A speedo reading 100 km/h may indicate a true speed of 95 to 98 km/h. In mph, the same reading is 62.1, but the true speed is 59 to 61 mph. GPS devices give the true speed, and the difference is a source of arguments over speeding tickets.
Fuel economy at speed
Fuel use rises steeply with speed. A car that burns 6 litres per 100 km at 90 km/h, which is 55.9 mph, uses 8 litres at 130 km/h, which is 80.8 mph, a rise of a third. In mpg terms, that is a fall from 39 to 29 mpg US. Tests quoted in both countries use different cycles, so figures cannot be directly compared even after a conversion.
Top speed and gearing
A car's top speed depends on power, drag and gearing. A top speed of 250 km/h at 6,500 rpm in top gear means that at 130 km/h, or 80.8 mph, the engine turns at about 3,380 rpm. Gear ratios are fixed, so engine speed and road speed are proportional. Reviewers sometimes give a table with rpm at 100 km/h and 70 mph, which are nearly the same speed.
More values for convert km/h to mph
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 = 0.0621371 mph
- 0.5 km/h = 0.310686 mph
- 3 km/h = 1.86411 mph
- 4 km/h = 2.48548 mph
- 7 km/h = 4.3496 mph
- 15 km/h = 9.32057 mph
- 20 km/h = 12.4274 mph
- 75 km/h = 46.6028 mph
- 200 km/h = 124.274 mph
- 500 km/h = 310.686 mph
- 2,000 km/h = 1,242.74 mph
- 10,000 km/h = 6,213.71 mph
Common slips when you convert km/h to mph
Multiplying by 1.609
From km/h to mph the number falls. If 100 km/h became 160, you used the wrong factor.
Confusing 0 to 60 mph with 0 to 100 km/h
The two benchmarks are different speeds: 96.56 km/h against 100 km/h. Compare them with care.
Mixing miles and nautical miles
A mile per hour is not a knot. A knot is 1.852 km/h and a mile per hour is 1.609 km/h.
Short answers
How do I convert km/h to mph?
Multiply by 0.6214.
What is 100 km/h in mph?
62.1 mph.
What is 130 km/h in mph?
80.8 mph.
How many km/h is 1 mph?
1.609 km/h.
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 km/h to ft/s, Convert km/h to knots, Convert knots to mph, Convert Mach to mph, Convert mph to m/s, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. The reverse direction is Convert mph to km/h.
In short, a “convert km/h to mph” calculation means multiplying by 0.6214 and writing the unit beside the answer. Your number is computed locally, with no account and no upload.