To convert mph to km/h, multiply by 1.609. To go the other way, multiply km/h by 0.621. So 60 mph is 96.6 km/h, and a 100 km/h sign means 62.1 mph. For quick maths at the roadside, remember that 8 km is almost exactly 5 miles.
That factor isn’t an approximation somebody picked. One international mile is defined as exactly 1.609344 kilometres, the figure NIST lists in its SI conversion factor tables. Everything below is that one number applied to the speeds you actually meet on the road, plus what to watch for when the signs switch units at a border.
mph to km/h conversion chart #
The limits you’ll see most on US and UK signs:
| mph | km/h |
|---|---|
| 15 | 24.1 |
| 20 | 32.2 |
| 25 | 40.2 |
| 30 | 48.3 |
| 35 | 56.3 |
| 40 | 64.4 |
| 45 | 72.4 |
| 50 | 80.5 |
| 55 | 88.5 |
| 60 | 96.6 |
| 65 | 104.6 |
| 70 | 112.7 |
| 75 | 120.7 |
| 80 | 128.7 |
km/h to mph conversion chart #
The limits you’ll see across Canada, Mexico, Europe, Australia and most of the world:
| km/h | mph | Where you’ll often see it |
|---|---|---|
| 30 | 18.6 | School and residential zones |
| 40 | 24.9 | Residential streets |
| 50 | 31.1 | Common urban limit |
| 60 | 37.3 | Urban arterial roads |
| 70 | 43.5 | Suburban and approach roads |
| 80 | 49.7 | Rural two-lane roads |
| 90 | 55.9 | Rural roads |
| 100 | 62.1 | Common highway limit |
| 110 | 68.4 | Faster highways and expressways |
| 120 | 74.6 | Motorways |
| 130 | 80.8 | Top motorway limit in several European countries |
Limits vary by country, province and state, so treat the right-hand column as a rough guide and trust the sign in front of you.
How do you convert mph and km/h in your head? #
You don’t need a calculator at the wheel. Three tricks cover almost everything.
mph to km/h: add 60 percent #
Take the mph figure and add 60% of it. For 50 mph that’s 50 + 30 = 80 km/h (exact: 80.5). For 70 mph it’s 70 + 42 = 112 km/h (exact: 112.7). The shortcut reads about half a percent low, less than 1 km/h at highway speed.
km/h to mph: the 5-and-8 rule #
8 km/h is almost exactly 5 mph, so divide by 8 and multiply by 5. 80 km/h is 50 mph, 120 km/h is 75 mph, and 100 km/h comes out at 62.5 (exact: 62.1). The error is about 0.6%, which is smaller than the gap between a typical car speedometer and your true speed. Multiplying by 0.6 is quicker but reads a little low: 100 km/h becomes 60 mph.
The Fibonacci trick #
The ratio between neighbouring Fibonacci numbers is about 1.618, very close to 1.609. So any two neighbours in 5, 8, 13, 21, 34, 55, 89, 144 give you a mph and km/h pair: 34 mph is about 55 km/h (exact: 54.7), and 55 mph is about 89 km/h (exact: 88.5).
Which countries use mph and which use km/h? #
The United States and the United Kingdom are the two big mph countries. Canada, Mexico, the Republic of Ireland, Australia, New Zealand and continental Europe use km/h, as does nearly everywhere else.
| Crossing | Speed signs change | Also changes |
|---|---|---|
| US to Canada | mph to km/h | Distances in km, fuel sold by the litre |
| US to Mexico | mph to km/h | Distances in km, fuel by the litre, pesos |
| UK to France (tunnel or ferry) | mph to km/h | You drive on the right |
| Northern Ireland to Republic of Ireland | mph to km/h | Distances in km, and the border is easy to miss |
The trap is that nothing in the car changes when you cross. A US-market car still shows mph in big numbers, and a UK car still reads mph on the autoroute. A speed limit sign usually shows only a number, not a unit.
Driving from the US into Canada or Mexico #
Learn five numbers before you cross: 50 km/h is 31 mph, 80 is 50, 90 is 56, 100 is 62 and 110 is 68. That covers almost every sign you’ll pass, and the full table is in the chart above.
Canadian limits are set by each province, so read the signs as you go. As a rough pattern you’ll see about 50 km/h in towns, 80 to 90 km/h on rural two-lane highways and 100 km/h on major divided highways, with some provinces posting higher limits on particular stretches. Mexico posts limits in km/h on all roads.
Most US cars with an analog dial print km/h on a smaller inner ring. Spend thirty seconds with it while parked: find 100 on that ring (just past 60 mph) and 50 (a little over 30 mph), and those two marks cover highway and town driving. Many digital clusters can switch the main readout to km/h in the vehicle settings, and your owner’s manual will name the menu. Rentals picked up on the Canadian side usually show km/h as the main scale, which flips the risk when you drive one back into the US.
What else changes at the border:
- Distances. “Toronto 100 km” is 62 miles, and an exit “2 km” ahead is about 1.2 miles.
- Fuel. Gas is sold by the litre. Multiply the price per litre by 3.785 for the price per US gallon, and remember the currency changes too.
- Mexican roads. Toll highways (cuota) are usually faster and better kept than free roads (libre). Watch for topes, speed bumps that can appear with little warning at the edge of towns.
- Coming home. Switch any speed app and alarm back to mph at your last stop before re-entering the US.
Your car’s speedometer probably reads a little high, so holding the mph equivalent on the dial usually keeps you at or slightly under the km/h limit. Don’t treat that as a buffer. Enforcement tolerance varies by country and province, and “I was converting” isn’t a defence.
Set up a speed app before the border #
A phone can show your speed in whatever unit the signs use, whatever the car’s dial says. Do all of this at your last stop before the crossing, not on the move.
- Mount the phone where you can see it with a quick glance, without it blocking your view of the road.
- Open Speedometer GPS and wait for the GPS pill under the number to read GOOD or EXCELLENT.
- Tap the unit button until it reads km/h. Trip distance switches to kilometres too.
- In Settings, turn on the speed limit alarm and pick the preset that matches the road you’ll join, such as 100 km/h for a major highway. Over that speed the readout turns red, the phone buzzes and beeps, and it repeats every ten seconds until you slow down.
- Leave it alone until your next stop.
The app works without mobile data, because the speed comes from GPS satellites rather than the network. That matters abroad, where roaming can be expensive or switched off entirely. Canadian provinces and most US states restrict handling a phone while driving, so any change waits for a stop or a passenger. How to switch a GPS speedometer between mph and km/h covers what else switches with the unit, and speed alert apps covers picking the limit.
The real risk is reading the wrong scale #
A few km/h of rounding never got anyone into trouble. Reading the wrong set of numbers does.
US cars show mph in big numbers with km/h on a small inner ring, and Canadian-market cars flip that. Drive a US car in Canada, mistake the big scale for km/h, and holding “100” puts you at 161 km/h in a 100 zone. Drive a Canadian rental in the US, hold 65 on the big km/h numbers under a 65 mph sign, and you’re doing about 40 mph on an interstate, which is dangerous in its own way.
Before you pull away in an unfamiliar car:
- Read the unit printed on the speedometer, not just the numbers.
- If the cluster is digital, check whether it can switch units, and do it while parked.
- Note the local limit in the car’s unit before the first sign, so you’re not converting in traffic.
Distance, fuel, knots and kph #
Speed limits aren’t the only numbers that change in metric territory.
| Unit | Conversion |
|---|---|
| 1 mile | 1.609 km |
| 1 kilometre | 0.621 miles |
| 1 US gallon | 3.785 litres |
| 1 UK (imperial) gallon | 4.546 litres |
| US mpg to L/100 km | 235.2 ÷ mpg |
| UK mpg to L/100 km | 282.5 ÷ mpg |
| 1 knot | 1.852 km/h or 1.151 mph |
| 1 m/s | 3.6 km/h or 2.237 mph |
A car that gets 30 mpg (US) uses 7.8 litres per 100 km. “km/h” is the official symbol, and “kph” is an informal abbreviation for the same thing. Knots matter if you use the same app on a boat: a nautical mile is exactly 1,852 metres, so 20 knots is 37 km/h or 23 mph. Knots vs mph for boat speed goes further.
Frequently asked questions #
Is 100 km/h the same as 60 mph? #
Close, but not quite. 100 km/h is 62.1 mph, and 60 mph is 96.6 km/h. If you hold 60 mph in a 100 km/h zone, you’ll be about 3.4 km/h under the limit.
What is 70 mph in km/h? #
112.7 km/h. That’s the top limit on many US interstates and UK motorways, just above the 110 km/h limit on some faster Canadian and Australian highways and well under a 130 km/h European motorway limit.
Is kph the same as km/h? #
Yes. Both mean kilometres per hour. “km/h” is the official symbol printed on speedometers and in regulations; “kph” is an informal abbreviation.
How do I change my car’s speedometer from mph to km/h? #
On an analog dial you can’t; read the smaller inner scale instead. Most digital clusters have a units option in the vehicle settings or trip computer menu, reached through the steering-wheel buttons or the touchscreen. Your owner’s manual names the exact menu.
Are Canadian speed limits in mph or km/h? #
Kilometres per hour, everywhere in Canada, and distances on road signs are in kilometres too. Mexico is the same. You can drive a US-market car with an mph speedometer there; you just have to keep to the posted km/h limits.