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km/h to mph Converter

Convert road speeds between km/h and mph, with the actual limits you will meet abroad.

Conversion table

SpeedIn mph
10.62137 mph
21.2427 mph
31.8641 mph
42.4855 mph
53.1069 mph
106.2137 mph
159.3206 mph
2012.4274 mph
2515.5343 mph
3018.6412 mph
4024.8549 mph
5031.0686 mph
6037.2823 mph
7043.496 mph
7546.6029 mph

🚦 Limits you will actually meet

  • 30 mph (UK town)48 km/h
  • 50 km/h (EU town)31 mph
  • 70 mph (UK motorway)113 km/h
  • 130 km/h (FR motorway)81 mph

Driving on the other scale

  • Mental shortcut: take 60% of the km/h figure and add a couple of per cent. 100 km/h is about 62 mph, 80 km/h about 50.
  • Going the other way, add 60%: 30 mph is 48 km/h and 70 mph is 113 km/h.
  • Most speedometers carry both scales, the secondary one in small figures inside the dial. Hire cars are the exception worth checking before you set off.
  • Speed limit signs in the United Kingdom and the United States are in mph without saying so; everywhere else they are km/h without saying so.

The conversion, and the shortcut worth memorising

One kilometre per hour is 0.621371 miles per hour, because a statute mile is 1,609.344 metres and a kilometre is 1,000. In the other direction, one mile per hour is 1.609344 km/h. Neither number is memorable, but the ratio is close enough to 0.6 that a useful trick exists: take away 40% to go from km/h to mph, and add 60% to come back. That puts 100 km/h at about 60 mph against a true 62.1 — close enough to know whether you are within a limit, and never so far off that it changes the decision.

Why your speedometer disagrees with GPS

Type-approval rules in Europe and most other markets say a speedometer may never display less than the true speed, but is allowed to display more — up to a percentage of the reading plus a fixed margin. Manufacturers therefore build in a deliberate optimism, and a car sitting on an indicated 100 km/h is often doing 94 to 97. GPS, which measures actual movement, is the honest one, and the gap between the two is not a fault. Tyre wear widens it further: a worn tyre has a smaller rolling radius, so the wheel turns more often for the same distance and the needle climbs.

Speed limits around the world

  • Urban limits: 50 km/h across most of Europe and Latin America, 30 mph (48 km/h) in the United Kingdom.
  • Many European cities have moved their default to 30 km/h, which is 19 mph.
  • Rural roads: 80–100 km/h in Europe, 55–65 mph (89–105 km/h) on comparable American roads.
  • Motorways: 120–130 km/h in most of Europe, 70 mph (113 km/h) in the United Kingdom, 65–85 mph in the United States by state.
  • Stopping distance grows with the square of speed: at 100 km/h a car needs roughly double the distance it needs at 70.
  • Germany's autobahn has an advisory 130 km/h on derestricted sections, which is 81 mph, not a limit but a recommendation.

Practical notes for driving abroad

  • In the United Kingdom, road signs and distances are in miles while fuel is sold in litres — the two systems coexist on the same trip.
  • Rental cars usually display the local scale first. Check which ring your needle is reading before the first roundabout.
  • Average-speed cameras measure between two points, so slowing only at the camera does not help.
  • Fuel consumption is quoted in L/100 km in Europe and mpg in the US and UK, and the two run in opposite directions: lower is better in one, higher in the other.
  • Cruise control set in the wrong unit is a common way to drift 60% over a limit; set it from the dashboard, not from memory.
  • Tyre speed ratings are printed in km/h even on cars sold in mph markets: an H rating means 210 km/h, or 130 mph.

Worked examples

The conversions a driver actually needs

A sign says 100 km/h

  1. 100 × 0.621371 = 62.1 mph
  2. Mental check: 60% of 100 is 60, plus a little
  3. Also 27.8 m/s, which is what a physics problem would want

100 km/h = 62.1 mph

A sign says 70 mph

  1. 70 × 1.609344 = 112.7 km/h
  2. Mental check: 70 plus 60% of 70 = 112
  3. Round up to 113 km/h on a metric speedometer

70 mph = 112.7 km/h

Frequently Asked Questions

How many mph is 100 km/h?

62.14 mph. The exact factor is 0.621371 miles per kilometre, because a statute mile is 1,609.344 metres. For a quick estimate on the road, take 60% and add a bit: 100 becomes about 62, 80 becomes about 50.

What is 70 mph in km/h?

112.65 km/h, which is why the British motorway limit is often quoted as 113. The conversion is exact: one mile per hour is 1.609344 km/h, so adding 60% to a mph figure lands you very close.

Why does my GPS show a lower speed than my speedometer?

Because speedometers are required by regulation never to under-read, but are allowed to over-read. Manufacturers therefore build in a margin, and an indicated 100 km/h is often a true 94 to 97. GPS measures actual movement between positions, so it is the more accurate of the two — and worn tyres widen the gap further.

Which countries use mph?

The United Kingdom and the United States are the main ones for road signs, along with a handful of territories such as Liberia, Myanmar and several Caribbean islands. Everywhere else posts limits in km/h, including Canada, Australia and all of continental Europe.

What is a quick way to convert km/h to mph in my head?

Halve the number and add a tenth of the original: 120 km/h becomes 60 + 12 = 72, against a true 74.6. Or take 60% for a slightly rougher figure. Going from mph to km/h, add 60%, so 50 mph becomes 80 km/h against a true 80.5.

Is 30 km/h the same as 30 mph?

No, and the gap matters in town. 30 mph is 48 km/h, while 30 km/h is only 19 mph. Confusing the two in a residential street is the difference between a survivable collision and a fatal one, which is why so many European cities set 30 km/h zones and label them clearly.

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