mph to km/h

How do I convert mph to km/h?

Multiply the speed in miles per hour by 1.609344 and you have kilometers per hour. That factor is exact, not rounded: the mile is defined as exactly 1,609.344 meters, so one mile per hour is exactly 1.609344 kilometers per hour. Every mph to km/h conversion on this page, in the converter above and in the tables below, is that one multiplication.

Key terms. mph (miles per hour) is the speed unit on US and UK road signs. km/h (kilometers per hour, also written kph or kmh) is the unit used on road signs in Canada, Mexico and most of the world. The international mile is 5,280 international feet of 0.3048 m each, which is where 1,609.344 m comes from. NIST, the US National Institute of Standards and Technology, publishes the official conversion factors.

Three worked examples:

• 25 mph (a typical US residential street): 25 × 1.609344 = 40.2 km/h
• 65 mph (many US interstates): 65 × 1.609344 = 104.6 km/h
• 80 mph (the top posted limit on some rural interstates): 80 × 1.609344 = 128.7 km/h

To use the converter at the top of the page, type a number in the Miles per hour box and the Kilometers per hour box fills in as you type. There is no Convert button. Tap the swap button (⇄) to go the other way, or use Copy to paste the answer into a text or spreadsheet. The “All units” grid shows the same speed in knots, meters per second, feet per second and Mach, and the mph to km/h quick table lists common speeds without typing at all.

Need the reverse? If you are reading a km/h sign and want to know the mph, our km/h to mph converter is built for that direction, with a full table of metric speed-limit signs. This page is for the opposite job: you know a speed in mph (your own car, a US limit, a pitch or a storm) and need to say it in km/h.

Popular conversions: 20 mph (32.19 km/h), 30 mph (48.28 km/h), 60 mph (96.56 km/h) and 100 mph to km/h (160.93 km/h), with UK limits and stopping distances. To convert a trip distance, see miles to km; for physics units, the mph to m/s converter (1 mph = 0.44704 m/s exactly).

Why is 1 mph exactly 1.609344 km/h?

Because since 1959 the foot has been defined as exactly 0.3048 meters, and a mile is 5,280 feet: 5,280 × 0.3048 = 1,609.344 meters. Divide by 1,000 meters per kilometer and the hours cancel, so 1 mph = 1.609344 km/h with no rounding anywhere.

NIST explains that “in 1959, the relationship of the foot to the meter was officially refined as 1 foot = 0.3048 meter exactly,” a change made to support US industry and trade with other countries. For decades a slightly different US survey foot survived in land surveying, but NIST declared it obsolete from January 1, 2023, so there is now just one foot and one mile in the US. NIST’s Special Publication 811 lists the resulting velocity factor, mile per hour to kilometer per hour, as 1.609344 exactly.

That matters for two practical reasons:

1. Round trips are clean. Because the converter uses the exact factor and only rounds what it displays, 65 mph converts to 104.6 km/h and back to exactly 65 mph. Converters that use a rounded factor such as 1.61 drift: 65 × 1.61 = 104.65, which converts back to 65.03 mph.
2. The reverse factor is the one that is rounded. 1 km/h = 1 ÷ 1.609344 = 0.621371192… mph, a never-ending decimal. That is why you see “0.621371” in km/h to mph formulas, but a clean 1.609344 in this direction.

Many top-ranking converters quote the factor as 1.60934, which drops the last digit. The error is tiny (about 0.00025%), but there is no reason to round when the exact value is only seven digits long.

mph to km/h conversion table

The table below converts the speeds people search for most, from 1 to 300 mph, using the exact factor and rounding to one decimal. The third column is what the mental shortcut (× 1.6) gives, so you can see how close it gets.

The example column is there to give each number a sense of scale; the speeds attached to trains, storms and sports are covered with their own sources on pages such as how fast trains go and how fast planes fly. The conversions themselves come straight from the factor.

Which is faster, 50 mph or 50 km/h?

50 mph is faster: it is 80.5 km/h, while 50 km/h is only 31.1 mph. For the same number, mph is always about 1.61 times faster than km/h, because a mile (1,609.344 m) is longer than a kilometer (1,000 m). The gap grows with the number, as the table shows.

So “is kph faster than mph?” has a simple answer: no, one km/h is the slower unit (0.621 mph). A car doing 60 on a km/h dial is moving at 37.3 mph, a town speed; the same 60 on an mph dial is 96.6 km/h, a highway speed. To go from km/h to mph, use the km/h to mph converter.

What is the easiest way to convert mph to km/h in your head?

Multiply by 1.6. It reads exactly 0.58% low at every speed, which is less error than most car speedometers already have. If multiplying by 1.6 is awkward, use one of the three tricks below.

The calculation behind that claim: 1.6 ÷ 1.609344 = 0.99419, so the shortcut is always 0.58% under the true value, whether you convert 5 mph or 500 mph. At 60 mph that is 96 km/h instead of 96.6; at 100 mph it is 160 instead of 160.9.

Trick 1: double it, then take off a fifth. Doubling gives × 2, and removing a fifth of the result gives × 1.6.

• 45 mph → 90 → 90 − 18 = 72 km/h (exact 72.4)
• 70 mph → 140 → 140 − 28 = 112 km/h (exact 112.7)

Trick 2: add half, then a tenth. 1 + 0.5 + 0.1 = 1.6.

• 50 mph → 50 + 25 + 5 = 80 km/h (exact 80.5)
• 35 mph → 35 + 17.5 + 3.5 = 56 km/h (exact 56.3)

Trick 3: the Fibonacci pairs. Consecutive Fibonacci numbers grow by a ratio close to 1.618, which happens to be near 1.609. So each number in the sequence, read as mph, is roughly the next one in km/h. We checked each pair against the exact factor:

From 5 mph upward the pairs are within about 1%, so “55 is about 89” is a handy anchor for a rural highway.

What is 65 mph in km/h, and what do US speed limits equal in km/h?

65 mph is 104.6 km/h. In general, US limits convert to awkward metric numbers: 25 mph is 40.2, 55 is 88.5 and 75 is 120.7 km/h. That is why US limits never line up neatly with Canadian or European ones.

US limits are set by each state and posted in mph. The table below takes the common posted values and adds the nearest “round” metric limit a driver might see abroad, to show how far apart they are.

Two patterns stand out. First, 50 mph ≈ 80 km/h and 75 mph ≈ 120 km/h are almost exact matches (within 1 km/h), which makes them easy anchors. Second, the common US interstate limit of 65 mph sits between the two typical metric freeway limits: faster than 100 km/h, slower than 110 km/h.

The same speeds in feet per second are useful for thinking about reaction distance: 60 mph is exactly 88 ft/s (26.8 m/s), and 70 mph is 102.7 ft/s (31.3 m/s). Our speed, distance and time calculator works out how far you travel at any of these speeds.

Driving in Canada: what do US speeds equal on km/h signs?

Every Canadian speed limit has been posted in km/h since September 1977, so a US driver needs to think in km/h the moment they cross the border. The usual limits are 50 km/h in towns (31.1 mph), 80 to 90 km/h on rural roads (49.7 to 55.9 mph) and 100 to 110 km/h on freeways (62.1 to 68.4 mph).

The Canadian Encyclopedia records that September 1977 brought “road signs showing distances in kilometres and speed limits in kilometres per hour,” and that, at the same time, cars with metric speedometers and odometers went on sale. Canada has stayed metric on its roads ever since, while the US and the UK kept miles.

Ontario, the province most US drivers enter through Detroit, Buffalo or the Thousand Islands, has been raising freeway limits from 100 to 110 km/h. Its June 2026 announcement added another 938 km of 110 km/h highway, rolling out through September 30, 2026, so that nearly 89% of the provincial highway network is posted at 110 km/h, up from 43%. Signs on a given stretch can still differ, so always go by what is posted.

Here is how your US habits translate on the Canadian side:

The row to watch is the rural two-lane road: a US driver comfortable at 55 mph is 8.5 km/h over an 80 km/h limit. The easy fix is to read the km/h scale on your speedometer directly rather than converting in your head.

Does my US car show km/h?

Many cars sold in the US show km/h as well as mph, usually as a smaller inner ring or a second number on a digital display. Many digital dashboards and infotainment screens let you switch the main readout to km/h in the settings menu, which is the simplest option for a Canada trip. If your car shows only mph, keep the converter on this page or the GPS speedometer open on a phone in a mount and switch it to km/h, with a passenger handling the phone.

If the dashboard and GPS disagree by more than a mile or two per hour, the GPS vs car speedometer guide explains why, and the speedometer calibration calculator works out your car’s exact error.

Where else do Americans need mph in km/h?

Beyond driving abroad, you convert mph to km/h whenever you talk to an audience outside the US and UK: travel, science homework, sports, weather and car specs. Most of the world, and all scientific writing, uses metric units.

• Renting a car in Europe, Mexico or Australia. Rental speedometers usually lead with km/h. Knowing that your usual 70 mph is about 113 km/h tells you where your comfort zone sits on the dial.
• Driving in the UK and Ireland. This one catches people out: the UK still posts limits in mph. GOV.UK lists the national limits for cars as 30 mph (48 km/h) in built-up areas, 60 mph (96 km/h) on single carriageways and 70 mph (112 km/h) on dual carriageways and motorways, with 20 mph (32 km/h) the default in Welsh built-up areas. Cross into the Republic of Ireland and the signs switch to km/h.
• School and college physics. Problems often give a car’s speed in mph and expect an answer in SI units. Convert to km/h with × 1.609344, or straight to meters per second with × 0.44704 (exact). The speed converter shows all units at once.
• Sports. International coverage of baseball pitches, tennis serves and running records quotes km/h. A 100 mph fastball is 160.9 km/h. Human sprinting speeds are covered on the how fast can a human run page, in both units.
• Weather. US forecasts give wind in mph, while many international agencies use km/h or knots. A 74 mph wind, the threshold of a Category 1 hurricane, is 119.1 km/h; for knots, the mph to knots converter does the same job.
• Car specifications. A US brochure’s “top speed 155 mph” is 249.4 km/h, which is how European reviews would describe the same car.

What is a treadmill speed in mph in km/h?

Multiply the treadmill’s mph by 1.609344: 3 mph walking is 4.83 km/h and 6 mph jogging is 9.66 km/h. US treadmills usually show mph and minutes per mile; gyms and apps elsewhere use km/h and minutes per km. This table converts both the speed and the pace, computed exactly.

Pace is 60 divided by the speed, so it is a different number in each unit system. For any pace not in the table, use the pace calculator.

Why does the US use mph instead of km/h?

Because US road signs, laws and speedometers were built around the mile, and the country never completed a switch to metric road signs the way Canada did in 1977. The mile itself is defined in metric terms (exactly 1,609.344 m), so the two systems are tied together precisely even though signs differ.

The practical upshot for anyone converting:

• Canada, Mexico and nearly all of Europe, Asia, South America, Africa and Oceania post limits in km/h.
• The US and the UK are the best-known countries still posting limits in miles per hour.
• Ships and aircraft everywhere use neither: they use knots, nautical miles per hour. One knot is 1.852 km/h exactly, about 1.15 mph. The knots to mph page covers that conversion, and boat speed explains why sailors kept it.

So even in the US, you will meet km/h on imported-car dashboards, in international news and in any science class, which is why a reliable mph to km/h converter is still worth having on your phone.

About this page

Every conversion on this page is calculated with the site’s tested conversion code (src/lib/convert.ts), which uses the exact definitions from NIST Special Publication 811: 1 international mile = 1,609.344 m, 1 foot = 0.3048 m. Numbers are rounded only for display. Speed-limit facts come from GOV.UK, The Canadian Encyclopedia and coverage of Ontario’s June 2026 provincial announcement, all linked in the sources below. Researched and written by Izhar Ahmad Danish; last updated October 25, 2026.