Most of the world measures driving speed in kilometres per hour, but a handful of countries — led by the United States and the United Kingdom — stick with miles per hour. If you drive, travel, or use a tracking app abroad, knowing how to convert between the two (and roughly which is which in your head) is genuinely useful. Here's the complete, practical picture.
The conversion, simply
The exact relationship is fixed: 1 mile = 1.609344 kilometres. So:
- To convert mph to km/h: multiply by 1.609 — e.g. 60 mph × 1.609 ≈ 97 km/h.
- To convert km/h to mph: divide by 1.609 (or multiply by 0.6214) — e.g. 100 km/h ÷ 1.609 ≈ 62 mph.
Quick mental math
You rarely need three decimal places while driving. Two handy shortcuts:
- km/h → mph: multiply by 0.6, or take roughly five-eighths. 120 km/h ≈ 120 × 0.6 = 72 mph (actual: 74.6, close enough to gauge it).
- mph → km/h: add half again plus a bit. 50 mph → 50 + 25 + 5 = 80 km/h (actual: 80.5).
A table of common driving speeds
The speeds you actually meet on the road, rounded for everyday use:
- 30 km/h ≈ 19 mph — European urban/residential limit (20 mph zones in the UK are 32 km/h).
- 50 km/h ≈ 31 mph — standard town limit across most of Europe.
- 80 km/h ≈ 50 mph — common rural road limit.
- 100 km/h ≈ 62 mph — expressway / dual carriageway limit in many countries.
- 112 km/h ≈ 70 mph — UK and US Interstate motorway limit.
- 130 km/h ≈ 81 mph — typical European motorway limit (France, Italy).
Which countries use which?
The overwhelming majority of the world — essentially all of continental Europe, Asia, Africa, South America, Australia, Canada, and most of the rest — uses km/h. The notable mph holdouts are:
- United States (mph everywhere)
- United Kingdom (mph for road speed, though it buys petrol in litres — a famous halfway measurement)
- A few smaller territories such as Liberia, Myanmar, and several island nations and US/UK dependencies
The UK is the curious case: it formally went metric for most things but kept miles and mph on its roads, so British road signs still read in miles while a litre of fuel and a kilogram of apples are standard.
A little history
The mile descends from the Roman mille passus — a thousand paces — later standardised in England as the statute mile of 5,280 feet. The kilometre arrived with the metric system born of the French Revolution in the 1790s, defined originally as one ten-thousandth of the distance from the equator to the North Pole. Over the 20th century most countries adopted metric road signage; the US and UK simply never made the switch on the road, largely because re-signing every road and re-educating every driver is enormously expensive and politically unpopular.
Why your app should handle both — and why metric underneath matters
If you use a GPS speedometer or tracking app, it should display in whichever unit you're used to, and switch instantly when you travel. But there's a subtlety good apps get right: they store and compute everything in one unit internally (almost always metric) and only convert at the moment of display. That avoids rounding errors creeping in when you toggle units, and keeps your saved trip history consistent no matter which unit you happened to be viewing at the time. PACE works this way — it's metric all the way down (km/h and km), converting to mph only on screen — so a trip you recorded in Germany reads correctly when you review it in mph back home.
A note on speedometer tolerance
Whichever unit you're in, remember your car's dashboard is calibrated to read slightly high so it never under-reports. A GPS reading, in either unit, is usually closer to your true ground speed — worth keeping in mind before you trust the dashboard to the last digit near a limit.
The takeaway
Multiply mph by 1.6 to get km/h, divide km/h by 1.6 to get mph, and memorise the handful of common limits above and you'll never be caught out abroad. And if you track your driving, pick a speed tracker that lets you flip between units freely while keeping your history rock-solid underneath — the best of both worlds.