Convert mph to km/h miles per hour ↔ kilometres per hour Free Online Secure
Type a value in miles per hour 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 from miles per hour
Convert to kilometres per hour
Common values — Convert mph to km/h (miles per hour ↔ kilometres per hour)
| mph | km/h |
|---|---|
| 1 | 1.609344 |
| 2 | 3.218688 |
| 3 | 4.828032 |
| 5 | 8.04672 |
| 10 | 16.09344 |
| 20 | 32.18688 |
| 50 | 80.4672 |
| 100 | 160.9344 |
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.
Crossing the border: miles per hour into km/h for the American road trip
An American family drives north to Toronto or south to Baja California. At the border, the signs stop speaking in miles per hour. The limit is 100, but not 100 mph: it is 100 kilometres per hour, which is about 62 mph. The cruise control, the speedometer and the instincts of years behind the wheel suddenly need a translation. To convert mph to km/h, multiply by 1.6093: 60 mph is 96.6 km/h, 70 mph is 112.7 km/h and 75 mph is 120.7 km/h. The calculator above multiplies as you type, and the sections below show how to keep a road trip safe and legal on both sides of the line.
You will find the rule with worked examples, a short profile of each unit, a comparison, a long set of cases from North American driving and the slips to avoid. The arithmetic runs in your browser, and what you type is not sent anywhere. Always follow the local limits and signs.
How to convert mph to km/h: multiply by 1.6093
The rule
One mile is exactly 1.609344 kilometres. To convert mph to km/h, multiply the figure in mph by 1.6093. So 30 mph is 48.3 km/h, 55 mph is 88.5 km/h and 85 mph is 136.8 km/h. To go the other way, multiply km/h by 0.6214.
Worked examples
A residential street at 25 mph is 40.2 km/h. A two-lane highway at 55 mph is 88.5 km/h. An interstate at 70 mph is 112.7 km/h, and a Texas stretch at 85 mph is 136.8 km/h.
Why 1.6093
The mile is defined as 1,609.344 metres, so the factor is exact. For quick work, 5 miles is 8 kilometres, so multiply by 8 and divide by 5.
A quick sanity test
The km/h figure is always 60 per cent bigger than the mph figure. If a “convert mph to km/h” calculation result is smaller, you used 0.6214 by mistake.
The mile per hour
The unit on American road signs
The mile per hour is the unit on road signs, speedometers and police radar in the United States. Signs carry only the number, because everyone in the country knows the unit. It is also used in the United Kingdom and a few territories.
Where it appears
American road signs, rental car dashboards, radar and speeding tickets.
The kilometre per hour
The unit on Canadian and Mexican signs
Canada and Mexico use kilometres per hour on all their roads, as does most of the world. Canadian signs show the number, and some include the abbreviation km/h. Distances on signs are in kilometres too, which adds a second conversion for American visitors.
Where it appears
Canadian and Mexican road signs, dashboards and police radar.
Miles per hour against kilometres per hour
One mph is 1.609 km/h, so any figure in km/h is bigger. A Canadian limit of 100 is much slower than an American limit of 100, because 100 km/h is 62 mph. A driver who forgets the difference and treats the sign as mph could drive at 161 km/h, a serious offence that a “convert mph to km/h” calculation would have prevented. The error runs in the other direction too: a Canadian visiting the US who reads 65 as km/h would crawl.
The factor is exact, so no rounding enters the conversion. The only trap is direction: from mph to km/h the number grows.
Where the conversion shows up
Driving in Canada
Canadian limits are typically 50 km/h in towns, 80 on rural roads and 100 on highways, with up to 110 on some. In mph that is 31, 50, 62 and 68. An American in a rental car keeps the needle on the km/h scale. If the car has a digital display, switching it to km/h removes mental arithmetic. A quick convert mph to km/h gives the equivalent of any sign.
Driving in Mexico
Mexican limits are about 110 km/h on toll motorways, 80 on federal highways and 40 in towns, with many local reductions. In mph, 110 is 68, 80 is 50 and 40 is 25. Speed bumps called topes appear without warning, and slowing from 80 km/h, or 50 mph, to a crawl is a daily routine in villages.
Trip planning
Distances are also in kilometres. Seattle to Vancouver is about 140 miles, or 225 km, and takes about two and a quarter hours at 100 km/h. Detroit to Toronto is 230 miles, or 370 km. Buffalo to Toronto is 100 miles, or 161 km. The time estimate works in either unit as long as speed and distance match.
Rental cars and dashboards
A car rented in Canada has a speedometer in km/h with miles in small print, or the reverse for a car brought from the US. A US-built car crossing the border has mph as the large numbers. Digital dashboards can switch units through the menu. If the car lacks that option, a simple rule helps: 100 km/h is about 62 mph, and 120 km/h about 75.
School buses and emergency vehicles
School zones in Canada are commonly 30 km/h, or 18.6 mph, when children are present, and 40 km/h, or 25 mph, at other times. Ambulances and fire trucks are not bound by the limit, but they expect other drivers to give way. If you see flashing lights, slow down and move to the side, whatever the unit on the sign.
Spreadsheet formulas
Place speeds in mph in column A and use =A2*1.609344 in column B. For the reverse, use =B2*0.621371. Add a column for travel time, =distance_in_km/B2. Label each column with its unit and use one decimal for the speed.
Rounding and precision
The factor is exact: 65 mph is 104.607 km/h. On a speedometer a whole number is enough, so 105. For a ticket calculation, the exact value is useful: 65 mph is 104.6, so a limit of 100 km/h is exceeded by 4.6. Carry the decimals until the end of a calculation and round only the final figure.
A mental shortcut
Add a half and a tenth. For 60 mph: 30 plus 6 gives 96, against an exact 96.6. For 70 mph: 35 plus 7 gives 112, against 112.7. Another approach is to double the mph and subtract 20 per cent, and for speeds near 60 mph the Fibonacci trick works: 5 miles is 8 km.
Landmarks to memorise
25 mph is 40 km/h, 30 mph is 48 km/h, 45 mph is 72 km/h, 55 mph is 89 km/h, 62 mph is 100 km/h, 65 mph is 105 km/h, 70 mph is 113 km/h and 75 mph is 121 km/h. These landmarks help you read Canadian and Mexican signs without calculation.
Reference ladder
15 mph is 24.1 km/h. 35 mph is 56.3 km/h. 50 mph is 80.5 km/h. 60 mph is 96.6 km/h. 80 mph is 128.7 km/h. 100 mph is 160.9 km/h. 120 mph is 193.1 km/h. 200 mph is 321.9 km/h. A ladder like this speeds up a check.
Checking by reversing
To check any convert mph to km/h result, multiply it by 0.6214. If 70 mph became 112.7 km/h, then 112.7 times 0.6214 is 70. A second test is the size: the km/h number is about 1.6 times the mph number.
Relation to m/s
1 mph is 0.447 m/s. A speed of 70 mph is 31.3 m/s, and 112.7 km/h is 31.3 m/s too. A driver who wants the distance covered in two seconds, the safe following distance, can use 62.6 metres. The units are different, but the physics is the same.
Stopping distances
At 100 km/h, which is 62 mph, a car needs about 84 metres to stop on dry asphalt, including reaction time. At 65 mph, or 105 km/h, it needs about 91 metres. At 75 mph, or 121 km/h, about 115. The extra 10 mph costs 25 metres, which is more than five car lengths. Speed saved is not worth the risk.
Time saved by speeding
On a 370 km trip, driving at 120 km/h instead of 100 saves about 37 minutes. The same trip in miles, 230 miles at 75 mph instead of 62, saves the same time. The gain is smaller than it feels, and the fuel cost rises by roughly a fifth. A “convert mph to km/h” calculation on the two speeds and a division show this at a glance.
Cruise control settings
On a Canadian highway set the cruise control to 100 km/h, which is 62 mph, or 110 km/h, which is 68 mph, where signed. In an American car in Canada the setting must be in km/h if the display shows it, and the arithmetic in the head is simple: the American 65 is about 105 km/h, 70 is 113 and 75 is 121. A “convert mph to km/h” calculation done once at the border avoids repeated checks.
Weather and visibility
In rain, fog or snow, reduce speed well below the limit. A drop from 100 km/h to 70 km/h, or from 62 mph to 43 mph, cuts stopping distance by roughly half. Canadian winter driving guidance suggests leaving at least four seconds of gap on snow. Rental companies in winter regions often provide winter tyres.
Wildlife and rural roads
On northern roads, moose and deer cross at dusk. Signs warn of wildlife and recommend lower speeds. At 80 km/h, which is 50 mph, a driver has more time to react than at 100 km/h, or 62 mph. Collisions with moose are often fatal, and speed is the main factor a driver controls.
Returning home
When you cross back into the US, switch the dashboard to mph and reset the cruise control. After a week in km/h, it is easy to drive at 100 on an American road, which is 100 mph and far too fast. Taking a minute at the border to change the display and say the new limit aloud keeps you safe.
Alaska and the northern highways
The Alaska Highway runs 1,387 miles, or 2,232 km, from British Columbia to Alaska, with limits of 90 or 100 km/h, which is 56 or 62 mph, in Canada and 55 to 65 mph in Alaska. Planning needs both units: fuel stops every 250 km, which is 155 miles, and signs in kilometres on the Canadian part. A “convert mph to km/h” calculation for each limit helps the driver settle into the rhythm.
Ferries and island roads
On islands such as Vancouver Island or Prince Edward Island, speeds are in km/h and roads are narrow, with limits of 50 or 80 km/h, which is 31 or 50 mph. Ferry schedules are fixed, so a driver estimating the drive to the terminal must convert speed and distance carefully. Arriving late costs a sailing, which is a better reason than a ticket to get the conversion right.
Speeding tickets across the border
Tickets issued in Canada to American drivers follow them. An excess of 20 km/h, which is 12.4 mph, over the limit is a modest fine, while 50 km/h, or 31 mph, over is a serious offence that may lead to licence suspension or vehicle impoundment in some provinces. Police use radar that shows km/h, and the limit on the sign is the legal limit.
Border queues and city driving
Within cities, Canadian limits of 50 km/h, 31 mph, and school zones of 30 or 40 km/h, which is 19 or 25 mph, are close to American patterns. Road works have limits of 60 to 80 km/h, or 37 to 50 mph. Misreading the unit in a school zone is more dangerous than on the highway, so slow down until you are sure.
Mountain passes and weather
Mountain highways in British Columbia and Alberta post advisory speeds on curves in km/h, for example 50 km/h, which is 31 mph, and winter limits are reduced. Drivers from the US, used to advisory speeds in mph, sometimes take the curves too fast. A quick conversion of each yellow sign is worth the effort, as the curves are tight and the drops are steep.
Fuel and distance
Fuel in Canada is sold in litres and distances are in kilometres, so consumption is in litres per 100 km. A car that gets 30 mpg US uses 7.8 L/100 km. At 100 km/h, or 62 mph, a trip of 370 km uses about 29 litres. Together with the speed, those are three conversions for the visiting driver, which is why a “convert mph to km/h” calculation is only the start.
Europe for American drivers
American drivers in Europe face the same conversion. A limit of 50 km/h in town is 31 mph, 90 km/h on rural roads is 56 mph and 130 km/h on a motorway is 80.8 mph. In Germany, some autobahn sections have no limit, but 130 km/h, or 81 mph, is the recommended speed. In the UK the signs are in mph, which is a relief for Americans but a surprise for others.
Speed cameras and apps
Navigation apps can be set to show speed in km/h or mph, and warn of speed cameras. If the phone is set to mph while the road signs are in km/h, the display confuses rather than helps. Set the app to the local unit before you cross the border, and check that the voice alerts use the same one.
Motorcycles and RVs
Motorcyclists touring from the US to Canada mostly ride at the limit, and a 2,000-mile trip becomes 3,219 km. An RV that cruises at 60 mph, or 96.6 km/h, is slightly under the Canadian highway limit of 100, a fine speed for fuel economy. Some provinces set lower limits for vehicles with trailers, typically 80 km/h, or 50 mph.
More values for convert mph 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 mph = 0.1609344 km/h
- 0.5 mph = 0.804672 km/h
- 3 mph = 4.828032 km/h
- 4 mph = 6.437376 km/h
- 7 mph = 11.265408 km/h
- 15 mph = 24.14016 km/h
- 20 mph = 32.18688 km/h
- 75 mph = 120.7008 km/h
- 200 mph = 321.8688 km/h
- 500 mph = 804.672 km/h
- 2,000 mph = 3,218.688 km/h
- 10,000 mph = 16,093.44 km/h
Common slips when you convert mph to km/h
Multiplying by 0.6214
From mph to km/h the number grows. If 70 mph became 43.5, you used the wrong factor.
Reading a Canadian sign as mph
A Canadian 100 means 100 km/h. Reading it as mph means driving 60 per cent too fast.
Mixing miles and kilometres in trip planning
A speed in km/h and a distance in miles give a wrong time. Convert one of them so that both match.
Short answers
How do I convert mph to km/h?
Multiply by 1.6093.
What is 60 mph in km/h?
96.6 km/h.
What is 70 mph in km/h?
112.7 km/h.
How many mph is 100 km/h?
62.1 mph.
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 mph to ft/s, Convert mph to knots, Convert knots to km/h, Convert m/s to km/h, Convert km/h to knots, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C. The reverse direction is Convert km/h to mph.
In short, a “convert mph to km/h” calculation means multiplying by 1.6093 and writing the unit beside the answer. Your number is computed locally, with no account and no upload.